[cff] 32bit integer overflow run-time errors 1/2 (#46149).

This commit handles the old engine.

* src/cff/cffgload.c: Include FT_INTERNAL_CALC_H.
(cff_decoder_parse_charstrings): Use OVERFLOW_ADD_LONG and
OVERFLOW_SUB_LONG where needed.

* src/cff/cffparse.c: Include FT_INTERNAL_CALC_H.
(power_ten_limits): New static array.
(do_fixed): Use it to prevent multiplication overflow.
(cff_parser_run): Use OVERFLOW_ADD_LONG.
3 files changed