* include/freetype/ftmm.h: Declare.
* include/freetype/internal/services/svmm.h (FT_Get_MM_Blend_Func):
New typedef.
(MultiMasters): New MM service function `get_mm_blend'.
(FT_DEFINE_SERVICE_MULTIMASTERSREC): Updated.
Update all callers.
* src/base/ftmm.c (FT_Get_MM_Blend_Coordinates,
FT_Get_Var_Blend_Coordinates): Implement.
* src/truetype/ttdriver.c: Updated.
* src/truetype/ttgxvar.c (TT_Get_MM_Blend): New function to handle
`get_mm_blend' service.
* src/truetype/ttgxvar.h: Updated.
* src/type1/t1driver.c: Updated.
* src/type1/t1load.c (T1_Get_MM_Blend): New function to handle
`get_mm_blend' service.
* src/type1/t1load.h: Updated.
* docs/CHANGES: Document.