This makes it possible to define an editable viewport outside of which the
contents are clipped.

One big benefit is that the getrect routine doesn't need to fetch the bboxes
of the shapes inside the viewport. It just needs the svg width, height, x,
y, and parent transform. It's also possible to add an optimized branch if
there is no parent transform specified.

One drawback is that the HTML5 method getBBox() includes the clipped content
in its calculation. That means the user will get scrollbars even though the
[draw svg] is clipping the contents which cause the scrollbars. Hopefully we
can just work around this by adding a "scrollbars" method for canvases to
just turn them off altogether.

Code for an experimental [draw array] is also added here. Combining it with
the viewport of [draw svg] will make it possible to interact with arrays of
widgets without the performance penalty normally associated with mouse
motion on Pd canvases.

Also:
* fixes some display bugs...

stray line where I forgot to change "data" to "d" that should have been part of bf11107b

for legacy drawing commands like [filledpolygon], don't scale the stroke (this is how it worked in Pd Vanilla)

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