stdio.h
suppresses "explicitly assigning a variable to itself warning" and potential unused parameter warnings
Added float cast to viewport size

Added float cast to remove compiler warnings.
gl2 size cast
STBI_NOTUSED
Fixed unused variables and scissor under zoom

- added NVG_NOTUSED to suppress unused param warnings
- fixed scissor anti-aliased border width when zoomed
Simplified back-end API a little

- removed assize from the back-end api
- moved image to paint in renderTriangles call
Added experimental GL3 back end which buffers whole frame
win32 changes.
Simplified attrib binding and removed color vertex attribute for a reasonable perf bonus.
Reversed path winding to make it actually ccw
Moved per call view uniform update to once per frame UBO update.
Corrected some spaces to tabs.
Move to using uniform buffer objects for fragment shader, which is set once per frame.
Fixed some warnings with MS compiler
Added support for line caps and joins
Do bevels only at control points