Icon-O-Matic: replace SVG parser with nanosvg

The parser was based on an old example from agg. NanoSVG is originally
based on the same code, but has lots of bugfixes. So it makes sense
to use it.

Nanosvg revision 25241c5a8f8451d41ab1b02ab2d865b01600d949

Fixes #5955, #8586, #13021.

Change-Id: I38ff9aa4e1d403c41979ebe42f7b45d4500a870c
Reviewed-on: https://review.haiku-os.org/c/haiku/+/2661
Reviewed-by: waddlesplash <waddlesplash@gmail.com>