Tksvg

TkSVG derived from SVGNano support of Tk8.7a5.
This aims any version of Tk8.6.

A successful "package require tksvg" is also possible on 8.7 now and is a no-op.
Thanks to Brad Lanam and Jan Nijtmans for the fruitful discussions.

Changes:

1) Bug fix: possible number overflow:
tk ticket: https://core.tcl-lang.org/tk/tktview?name=822330269b
tksvg ticket: https://github.com/oehhar/tksvg/issues/14

2) Upstream fix from nanosvg
179: "Division by float 0"

3) pckIndex.tcl changed to load in tk8.7 as a no-op

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Release 0.7 is synchronized with current tk trunk.
Changes:
- svgnano patch for number interpretation: .4 is accepted as float
- use the Androwish alternate solution for a big file pretest for svg files.

Thanks to Brad Laham for Linux32 and Darwin64 binaries.