For internal use; we want to share code between the forthcoming CFF2
support and TrueType.
* include/freetype/internal/services/svmm.h (FT_Done_Blend_Func):
New typedef.
(MultiMasters): Add `done_blend'.
(FT_Service_MultiMasters): Updated.
* src/truetype/ttgxvar.c (tt_done_blend): Use `TT_Face' as argument.
* src/truetype/ttgxvar.h: Updated.
* src/truetype/ttobjs.c (TT_Face_Done): Updated.
* src/truetype/ttdriver.c (tt_service_gx_multi_masters): Updated.
* src/type1/t1driver.c (t1_service_multi_masters): Updated.