[truetype] Integer overflows.

Reported as

  https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=2270
  https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=2278

* src/truetype/ttinterp.c (Ins_MDRP, _iup_worker_interpolate): Use
ADD_LONG and SUB_LONG.
2 files changed