[truetype] Add framework for TrueType properties.

* src/truetype/ttdrivr.c: Include FT_SERVICE_PROPERTIES_H.
(tt_property_set, tt_property_get): New functions, still empty.
Define `tt_service_properties' service.
Update `tt_services'.

* src/truetype/ttpic.h: Include FT_SERVICE_PROPERTIES_H.
(TT_SERVICE_PROPERTIES_GET): New macro.
(TTModulePIC): Add `tt_service_properties'.
3 files changed