[autofit] Minor speedup of reverse charmap creation. * src/autofit/afglobal.h (AF_HAS_CMAP_ENTRY): New flag. (AF_STYLE_MASK): Update value. * src/autofit/afglobal.c (af_face_globals_compute_style_coverage): Set `AF_HAS_CMAP_ENTRY`. * src/autofit/afadjust.c (af_reverse_character_map_new): For the creation of the reverse map, change code to handle glyphs with cmap entries before glyphs without cmap entries. Doing so avoids some code redundancy and reduces the number of hash lookups.