The code simply uses the MM functions from the `truetype' module.
Everything is guarded with TT_CONFIG_OPTION_GX_VAR_SUPPORT.
* include/freetype/internal/tttypes.h (TT_Face): New field `mm'.
* src/cff/cffdrivr.c: Include FT_SERVICE_MULTIPLE_MASTERS_H.
(cff_set_mm_blend, cff_get_mm_blend, cff_get_mm_var,
cff_set_var_design, cff_get_var_design): New functions.
(cff_service_multi_masters): New service.
(cff_services): Updated.
* src/cff/cffload.c (cff_get_var_blend, cff_done_blend): New
functions.
* src/cff/cffload.h: Updated.
* src/cff/cffpic.h (CFF_SERVICE_MULTI_MASTERS_GET): New macro.
* src/sfnt/sfobjs.c: Include FT_SERVICE_MULTIPLE_MASTERS_H.
(sfnt_init_face): Initialize `face->mm'.