Add callbacks for inter-module calls.

NOTE: Does not compile!

* include/freetype/internal/psaux.h: Add function pointer
declarations.

* src/psaux/cffdecode.c (cff_decoder_init): Update to take in
callbacks.
* src/psaux/cffdecode.h: Ditto.

* src/cff/cffgload.c (cff_compute_max_advance, cff_slot_load):
Update calls to pass in callbacks.
* src/psaux/cf2ft.c, src/psaux/cffdecode.c: Use them.
6 files changed