'aggraef/purr-data-abstractionsaving-final-fix'

This is broken right now in Testing and Unstable, the fix should still
work in Debian Stretch, Ubuntu Xenial and later.

Instead of casting a magic number to a pointer, which is a sure recipe
for disaster, provide a properly initialized dummy t_canvasenvironment*
pointing to static storage.

This uses findAndReplaceDOMText(), which apparently looks for
case-sensitive matches, but the search text entered by the user is
*always* converted to lowercase. This means that mixed case search terms
just won't be found, which is bad. (E.g., try searching for "GEM" in the
toc to see this bug in action.)

Fixed by just removing the call to toLowerCase() on the search text,
case-sensitive searches now work as expected, problem solved.

This resolves a long-standing bug (the relevant code is 4-5 years old).
While it is just one little missing check in the keyboard event handler,
which is surely just an oversight, this has the dire consequence of
breaking navigation with the Tab key.

- The root cause for this issue is in the document.body event listener
  callback, where we always reset the focus to the search text input if
  there's *any* keyboard input (other than a LF or CR on the file
  browser and bookmark buttons) while the focus is on something
  else (such as an item in the toc or in the search results). The
  intention there surely was to enable the user to just start
  typing *anywhere* in the dialog, which is convenient, but has the
  unwanted side-effect of breaking Tab navigation (as well as the cursor
  keys).

- The fix is simply to *not* reset the focus if the key event is the Tab
  key. Besides Tab, we also treat the modifier and cursor keys in the
  same fashion, so that these will be handled on the spot rather than
  being forwarded to the search text input. By these means, you can
  still start typing your search terms from anywhere in the dialog, but
  navigation with Tab and Shift+Tab and the cursor keys now also work as
  expected.

- Also, why is the div holding the toc items created again and again for
  each item in display_toc()? I moved the corresponding statement,
  div = document.createElement("div"), right before the toc.forEach()
  loop now, which I think is where it really belongs.

This reverts commit 12bd57bd, reversing
changes made to e9d38d23.

Disable the bookmark icon in situations where bookmarking isn't possible (search results, doc directory).

- Use canonical paths just about everywhere in the help browser. We want
  to stick to portable, normalized paths as much as possible, to avoid
  funky Windows path names, especially in bookmark files which should be
  portable across different platforms.

- Fix the generated click_toc() call in display_toc(); we need to
  properly stringify the callback argument there.

- Update the search field after opening a directory via the file
  browser, so that the search text matches the directory display. Is
  there a reason that we're not already doing this? I don't think so,
  because we're doing the same when clicking a link in the toc.

- Prevent the doc directory from being bookmarked. There's nothing
  interesting to see there anyway (just subdirectories, no help
  patches). Also, since the toc lives there (in a virtual sense, i.e.,
  the current browser directory is set to this directory whenever the
  toc is displayed), we also avoid an interesting race condition which
  arises if we try to update the toc while we're displaying it. (This
  doesn't seem to happen on all platforms, but I've seen it on the Mac
  at least.)

- Fix a purely cosmetic issue with the bookmark entries. (Entries with a
  null description were stored as is and then written to the bookmarks
  file. Now the description is just omitted in that case.)

This takes the form of a little bookmark icon to the right of the file
browser icon. Just the plain icon indicates that the current directory
hasn't been bookmarked yet, and that clicking on it will bookmark it.
If you do this, a little red cross appears on the icon, which reminds
you that the directory has been bookmarked, and that clicking on the
icon will remove the bookmark again.

Note that in general a directory may have been bookmarked multiple
times, by using the keyboard shortcut (Ctrl-D). In this case the red
cross will stick until the last instance of the bookmark has been
removed.

The icons come from the Manjaro KDE Breath theme (a variation of the
KDE Breeze theme), and we also replaced the folder icon with a matching
icon from the same theme. Thanks are due to the Manjaro and KDE teams!

While we were at it, we also fixed the vertical alignment of the icons
with respect to the search field, they are properly aligned to the
middle now.

The Ctrl+D keyboard command in the help browser adds a bookmark for the
current browser directory, Shift+Ctrl+D removes it again. Note that the
same directory can be bookmarked multiple times (using Ctrl+D), in which
case the same number of delete commands (Shift+Ctrl+D) are required to
delete all instances of the bookmark again; at any time, the oldest
instance will be removed first.

This also provides a (really simplistic) way to reorder bookmarks, since
you can re-add an existing bookmark and delete its older instance
afterwards, which effectively moves the bookmark to the end of the
bookmarks section. It goes without saying that this becomes rather
laborious if you have to manage a lot of bookmarks, so in that case you
might prefer to just edit the bookmarks file (see below) in your
favorite text editor instead.

Bookmarks are shown in their own "Bookmarks" section at the bottom of
the toc, after the built-in toc sections. The "Bookmarks" section title
will be visible only if there are any bookmarks. As with the built-in
toc items, clicking on the title of a bookmark takes you to the
corresponding directory, which may be in the doc or extra hierarchy, or
anywhere else on your hard disk. If a <dir>-meta.pd file in pddp format
is present in the bookmarked directory, the browser will try to extract
title and description from the NAME and DESCRIPTION tags in that file,
otherwise it simply uses the basename of the directory as title and
leaves the description empty.

The bookmarks are stored permanently on disk as a JSON file in the users
home directory, named .purr-data/bookmarks.json on Linux and the Mac,
and AppData/Roaming/Purr-Data/bookmarks.json on Windows. This file is
read each time the help browser opens, so the bookmarks persist across
program invocations, and you can even edit the file manually and reopen
the help browser to make it pick up your changes while Purr Data keeps
running.

This saves time and bandwidth.

Closes jwilkes/purr-data#668

Previously we would redownload the tarball in all cases, saving it
as nwjs-*.tar.gz.1 or similar.

This helps the CI to discover the necessary nw.js tarball while keeping
the logic in one place.

This allows the CI to cache the downloaded tarball. Developers can
manually delete it if needed.

This causes tar_em_up.sh to download an older version of nw.js suitable
for OSX 10.8.

Features:

- Rebuilds and caches the search index if there is no cache yet, or if
  the cache is outdated (i.e., any cached directory or its parent was
  removed or modified since the cache was last created).

- Keeps track of the modification times of all cached directories of
  help files, as well as their parent directories, in order to determine
  when the cache is outdated. The parents are tracked to catch changes
  where new sibling directories are added. This may produce some false
  positives and still isn't 100% foolproof, but it is as close as we can
  get if we still want to achieve substantial speedups.

- Automatically rebuilds the index (and cache) from scratch, as soon as
  the help browser is relaunched after changes to the browser
  configuration in the gui prefs. So there's no need any more to
  relaunch Purr Data to have these changes take effect.

Both the index cache and the directory timestamps are maintained as
ordinary text files with a straightforward syntax (basically
colon-delimited csv) in the user's home directory. The files are located
in configuration directories (.purr-data on Linux and Mac,
AppData/Roaming/Purr-Data on Windows). Thus it's easily possible to
modify these files with external tools (e.g., if we want to upgrade the
file format in the future.)

add an alert system that notifies the user of the existence of unsaved edited instances of the abstraction he is editing or about to edit

Our 32 bit Windows installer currently installs some binaries (dll and
exe files) in the Windows system32 directory. This is unnecessary (all
required dlls are already in the program bin directory where pd.exe will
readily find them), and actually a nuisance, since we currently don't
remove some of the dlls in system32 again when uninstalling, causing a
lot of inconvenient prompts from the installer when upgrading or
reinstalling.

If the user wants to run cyclist, pdreceive, or pdsend from whatever
command line he uses, he can easily add the program bin directory to
PATH himself. That's much better than having our installer pollute the
system32 directory.

The mingw64 build already does it that way, here we simply apply the
same fixes to the mingw32 build.