[autofit] Allocate AF_Loader on the stack instead of AF_Module.

Stop sharing a global `AF_Loader'.  Allocate one on the stack during
glyph load.

Right now this results in about 25% slowdown, to be fixed in a
following commit.

With this patch loading glyphs from different faces from different
threads doesn't immediately crash in the autohinting loader code.

Bugs:

  https://bugzilla.redhat.com/show_bug.cgi?id=1164941

* src/autofit/afloader.c (af_loader_init): Pass
`AF_Loader' and `FT_Memory' instead of `AF_Module' as arguments.
(af_loader_reset, af_loader_load_glyph): Also pass `loader' as
argument.
(af_loader_done): Use `AF_Loader' instead of `AF_Module' as
argument.

* src/autofit/afmodule.c (af_autofitter_init): Don't call
`af_loader_init'.
(af_autofitter_done): Don't call `af_loader_done'.
(af_autofitter_load_glyph): Use a local `AF_Loader' object.

* src/autofit/afloader.h: Include `afmodule.h'.
Update prototypes.
Move typedef for `AF_Module' to...

* src/autofit/afmodule.h: ... this place.
No longer include `afloader.h'.
5 files changed