fix a crasher with gtemplate_new dereferencing a freed pointer, and harden rule for creating a struct

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)

fix some nasty regressions with drawnumber and drawsymbol due to Ivica and I overlooking fairly obvious compiler warnings :(

port 9ab1b10476bca7e3998d5bf907296979dfc6e558 from Pd-l2ork: fixed regression where canvaslist was not properly stored

bind/unbind scalar symbol in scalar_vis instead of scalar_new
This way scalar events continue to work if the user happens to
change the [struct] arguments on us.

make [draw] arguments more closely follow the svg spec
* [draw circle 20 1 2]: radius=20, xcenter=1, ycenter=2
* [draw rect 5 10 20 40]: width=5, height=10, xoffset=20, yoffset=40
* [draw ellipse 5 10 20 40]: xradius=5, yradius=10, xcenter=20, ycenter=40

code for this is ugly (i.e., repetitive) and can probably be easily abstracted/refactored...

add a flag to drawsymbol/number visfn to allow updating existing objects instead of having to erase/redraw them

Make it possible to just send new attributes to GUI for [drawpolygon] and friends when a field value changes
(This performs better than erasing and redrawing the scalar in the GUI)