[cff, pshinter] Clean up unsigned counters.

Loops with unsigned decrement can be reliably stopped when the counter
wraps around after reaching zero.

* src/cff/cffload.c (cff_charset_compute_cids): Use unsigned counter.
* src/pshinter/pshalgo.c (psh_hint_table_activate_mask): Ditto.
* src/pshinter/pshrec.c (ps_mask_table_merge): Ditto.
3 files changed