* coding.c: Integer and buffer overflow fixes.

* coding.c: Integer and buffer overflow fixes.

(Funencodable_char_position, Fcheck_coding_systems_region)
(get_translation, handle_composition_annotation, consume_chars):
Use ptrdiff_t, not int, to avoid needless 32-bit limit on 64-bit hosts.
(consume_chars): Rewrite to avoid calculating an address outside buffer.