first draft for opening files from command line or graphical file manager in the current Purr Data instance

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)

quick fix for backslashes in legacy tcl commands breaking the GUI parser-- just send "dummy" command arg

escape "\r" coming from Pd before evaluating

fix regression where Pd would eat the first character of a symbol if the symbol contained a double quote.

(I forgot to actually test the branch that handles strings with quotes in them)

allow this to work:
gui_start_vmess("foo", "");
gui_start_array();
gui_s("hello");
gui_end_array();
gui_end_vmess();

In other words, a gui message with a single array argument. There should rarely be a need for this (if at all), but it should still send a well-formed message to the GUI (which it wasn't before this bug fix)

add boilerplate for keeping track of toplevel Pd canvases in the GUI. While the GUI knows all the open windows, it can't tell the difference between a Pd toplevel and a subpatch. I'm not sure why the difference is important, but this interface supplies that info to the GUI.

change alarm bell kludge used to separate messages to the GUI to a "unit separator" kludge. Still bad, but a little less bad

simplify GUI-side parser, and send raw (i.e., old) sys_vgui and sys_gui calls to just post to the console

add note in todo about potential loss of data when > 4096 bytes of data
are entered into a message box and sent to Pd

changed the GUI message parser to try to deal with newlines and old style tcl messages at the same time

implemented iemgui "pos" method