Don't assume that stated character widths fit in int.

Don't assume that stated character widths fit in int.

* character.c (Fchar_width, c_string_width, lisp_string_width):
* character.h (CHAR_WIDTH):
* indent.c (MULTIBYTE_BYTES_WIDTH):
Use sanitize_char_width to avoid undefined and/or bad behavior
with outlandish widths.
* character.h (sanitize_tab_width): Renamed from sanitize_width,
now that we have two such functions.  All uses changed.
(sanitize_char_width): New inline function.