* coding.h (struct coding_system): Make safe_charsets a pointer to

* coding.h (struct coding_system): Make safe_charsets a pointer to
unsigned char.
* coding.c (CODING_ISO_REQUEST): Check for safe_charsets content
being 255.
(SAFE_CHARSET_P): Likewise.
(setup_iso_safe_charsets): Properly setup safe_charsets.
(Fdefine_coding_system_internal): Likewise.
(setup_coding_system): Likewise.  Remove unneeded casts.
(detect_coding_iso_2022): Compare Viso_2022_charset_list with
CODING_ATTR_CHARSET_LIST, not CODING_ATTR_SAFE_CHARSETS.  Remove
unneeded casts.