(ENCODE_UNSAFE_CHARACTER): Adjusted for the name change

(ENCODE_UNSAFE_CHARACTER): Adjusted for the name change
of CODING_REPLACEMENT_CHARACTER.
(decode_coding_iso2022): If CODING_FLAG_ISO_SAFE, set
CODING_MODE_INHIBIT_UNENCODABLE_CHAR flag in coding->mode, and
check this flag on encoding.
(encode_coding_sjis_big5): Check
CODING_MODE_INHIBIT_UNENCODABLE_CHAR flag of coding->mode.
(Fset_terminal_coding_system_internal): Set
CODING_MODE_INHIBIT_UNENCODABLE_CHAR flag in terminal_coding.mode
instead of setting CODING_FLAG_ISO_SAFE flag in
terminal_coding.flags.