This patch makes it possible to have multiple running instances of Purr Data,
and to leverage that interface from Pd-l2ork to get [pd~] working on all
platforms

Some difficulties required revisions to [pd~] in Pd Vanilla's code
* use quoted path args for Windows when starting the [pd~] subprocess
* replace sys_havegui() from Pd Vanilla's recent "threadening" with sys_nogui

The "-unique" flag requires the OSX app bundle to be able to start by calling
the binary in Pd-l2ork.app/Contents/Resources/app.nw/bin/pd-l2ork. This should
also make it possible to run Purr Data on OSX both by using an app bundle
(where the GUI starts the Pd process) and by installing and running from the
command line (where the Pd process starts the GUI)

The "--user-data-dir" flag sets the directory for various nw.js state used
by a running instance. To prevent races nw.js requires that each running
instance have its own directory that is not shared with any other instances.

Setting the value for this flag has two important potential side-effects:

1. If you have a running instance and try to start an additional instance
   that has the same data directory, nw.js will just send an "open" event
   the first running instance and exit the 2nd instance gracefully. This is
   the default nw.js behavior and the default Pd-l2ork behavior as well.
2. If you have a running instance and try to start an additional instance
   with a different data directory than the first, you'll get a fully
   functional 2nd instance of nw.js running. This is the behavior we desire
   when the user runs pd-l2ork with the "-unique" flag.

In each case we set the data dir explicitly in order to get consistent
positional command line arguments in the GUI.

In normal mode Purr Data will use the default data dir as specified in the
nw.js docs for the particular platorm. Since the same default dir is used
each time Purr Data is run, there will be only one data dir that gets created.

When run with the "-unique" flag, Purr Data will append "-$portno" to the
default data directory, where $portno is the port Pd chose to communicate
with the GUI. That ensures that each separate instance of Purr Data can
get a unique data dir.

A side effect is that users may end up generating multiple data dirs that
don't get deleted on exit. But Pd starts searching for available ports in the
same range each time, and unless the user tries to run hundreds of instances
at once this directory spam shouldn't be too big of a problem.

sys_expandpathelems: replacement for @pd_help should be the last element on the path, not the first.

These bugs were discovered via static code-analysis
https://scan.coverity.com/projects/pure-data-pure-data
(The CID numbers are the "Coverity IDs" used to identify the various bugs)

- Don't free binbuf within glist_readfrombinbuf (CID:74871)
- it must be deleted by the caller
- Initialize sockaddr_in (CID:74861,74862,74863,74866)
- Initialize indelay/outdelay (CID:74864,74865)
- Initialize device-arrays (CID:74853,74854,74855,74856)
- Closing unneeded sockets (CID:74827)
- Initialize sockaddr_in (CID:74860}
- Close file-descriptor if the soundfile is unparsable (CID:74822,74823)
- Close file-handle in cleanup (CID:74816)
- Call va_end() when handling variadic args (CID:74872)
- Added missing break (CID:74800)
- Prevent NULL-dereferences (CID:74792,74793)
- Size checks when copying into string buffers (CID:74844,74845,74846,74847,74849)
- Freeing no-more used storage (CID:74832)
- Fixed code block (CID:74806)
- Initialize sockaddr_in (CID:74860)
- Initialize array-values to 0 (CID:74867)
- Free allocated memory (CID:74813,74830)
- Removed allocation of unused memory
- Use pd_free() to free templates (CID:74814)
- template_free() does not free the entire structure (it misses the pd_new() part)
- initialize variable (CID:77865)
- Prevent NULL-pointer dererencing (CID:77864)
- Free heap-allocate binbuf after use (CID:74833)

very stupid kludge just to get the code to compile on Windows-- this needs to get fixed by a more complete backport of Pd Vanilla's s_path.c code

(manually ported)
*added @pd_help in addition to the existing @pd_extra that can be used for paths
*made pddplink capable of parsing @pd_extra and @pd_help
*updated cyclone help files to make advantage of the @pd_extra/@pd_help paths in order to reference global help file documentation

*backported vanilla patch http://sourceforge.net/p/pure-data/pure-data/ci/f535c339c99a74edb3920c2e630500df128b7d8f/

*Ported open_via_helppath from pd to fix inability to open help files when starting pd-l2ork from the doc/5.reference folder.

fixed regression where empty image box appeared on gop-ed parent in incorrect locations and/or it was not supposed to show up at all. Some refinements to the path detection/removal of debug output.

revamped path to support ~/, root paths, relative paths, as well as special tags like @pd_extra that expands to the location of the extra folder (other tags may be added later if necessary).

streamlined @pd_extra parsing for easier integration with other file open calls including externals. Added it to open_via_path

fixed noselect bug when line is selected and one clicks on a blank canvas which should also deselect selected line. also made pd_extrapath struct global as part of s_stuff.h so that ggee/image can use dynamic descriptors for retrieving of files (.e.g @pd_extra is translated to the pd's system-wide location of the extra/ folder)

working on new dialog windows
updates to 14.partialtracer and sigmund~

bug fixes