[autofit] Updated to reduce casting.

* src/autofit/afglobal.h (AF_FaceGlobalsRec): Change `glyph_count` type.
* src/autofit/afglobal.c (af_face_globals_compute_style_coverage,
af_face_globals_get_metrics, af_face_globals_is_digit,
af_face_globals_new): Changed local types and updated accordingly.
* src/autofit/aflatin.c (af_latin_metrics_init_blues): Ditto.
3 files changed