[sfnt] PaintRotate/PaintRotateAroundCenter spec updates

* src/sfnt/ttcolr.c (read_paint): Implement spec change where
PaintRotate and PaintRotateAroundCenter were split for a more
compact format definition.  Update parsing to read shorter values
as changed in the spec.
* include/freetype/ftcolor.h (FT_PaintRotate): Update documentation.
2 files changed