Synchronize with FreeType.
This patch contains the following commits.
48c77da3 Add minor comment to avoid confusion (#19044).
255828c8 [autofit] Fix Emscripten crash (patch #9180).
d44daf9e * src/truetype/ttgxvar.c (TT_Vary_Apply_Glyph_Deltas): Thinko.
4441f7b2 Replace `foo == NULL' and `foo != NULL' with `!foo' and `foo', resp.
84b0d992 */*: Use `0.5f' for tracing 16.16 numbers.
31f80553 [autofit] Avoid uninitialized jumps (#50191).
0a1169f7 * src/autofit/afglobal.c (af_face_globals_free): Erase useless code.