Add function `FT_Get_GlyphLayers' to access `COLR' table data.

* include/freetype/internal/ftobjs.h (FT_Glyph_LayerRec): Move this
structure to...
* include/freetype/freetype.h (FT_Glyph_LayerRec): ... this
header file.
(FT_Glyph_Layer): New typedef.
Update code to use it where appropriate.

* src/base/ftobjs.c (FT_Get_GlyphLayers): New function.
8 files changed