[base, cff, truetype] Integer overflows.

Reported as

  https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=2060
  https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=2062
  https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=2063
  https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=2068

* src/base/ftobjs.c (ft_glyphslot_grid_fit_metrics): Use
OVERFLOW_ADD_LONG and OVERFLOW_SUB_LONG.

* src/cff/cf2blues.c (cf2_blues_capture), src/cff/cf2hints.c
(cf2_hintmap_adjustHints): Use OVERFLOW_SUB_INT32.

* src/truetype/ttgload.c (compute_glyph_metrics): User
OVERFLOW_SUB_LONG.

* src/truetype/ttinterp.c (Direct_Move, Direct_Move_Orig,
Direct_Move_X, Direct_Move_Y, Direct_Move_Orig_X,
Direct_Move_Orig_Y, Move_Zp2_Point, Ins_MSIRP): Use
OVERFLOW_ADD_LONG and OVERFLOW_SUB_LONG.
6 files changed