(LEADING_CODE_8_BIT_CONTROL, CHARSET_8_BIT_CONTROL,

(LEADING_CODE_8_BIT_CONTROL, CHARSET_8_BIT_CONTROL,
CHARSET_8_BIT_GRAPHIC): New macros.
(SINGLE_BYTE_CHAR_P): Make it faster by using casting.
(CHARSET_ISO_GRAPHIC_PLANE): Use XINT instead of XFASTINT.
(CHARSET_REVERSE_CHARSET): Likewise.
(CHARSET_VALID_P): Handle new charsets; eight-bit-control and
eight-bit-graphic.
(BYTES_BY_CHAR_HEAD, WIDTH_BY_CHAR_HEAD): Optimize for ASCII.
(CHAR_CHARSET, MAKE_CHAR, SPLIT_CHAR, CHAR_BYTES): Likewise.
(PARSE_MULTIBYTE_SEQ) [BYTE_COMBINING_DEBUG]: Abort if we
encounter an invalid multibyte sequence.
(PARSE_MULTIBYTE_SEQ) [not BYTE_COMBINING_DEBUG]: Assume multibyte
sequence is always valid.
(MAKE_NON_ASCII_CHAR, SPLIT_NON_ASCII_CHAR): These macros Deleted.
(UNIBYTE_STR_AS_MULTIBYTE_P, MULTIBYTE_STR_AS_UNIBYTE_P): New
macros.
(CHAR_STRING): For 8-bit characters, call char_to_string.
(INC_POS) [not BYTE_COMBINING_DEBUG]: Faster version.  Assume
multibyte sequence is always valid.
(BUF_INC_POS) [not BYTE_COMBINING_DEBUG]: Likewise.
(parse_str_as_multibyte, str_as_multibyte, str_to_multibyte,
str_as_unibyte): Extern them.
(BCOPY_SHORT): Fix a bug.
(CHAR_LEN): This macro deleted.  Callers changed to use
CHAR_BYTES.
(FETCH_STRING_CHAR_ADVANCE): Check multibyteness of STRING.
(FETCH_STRING_CHAR_ADVANCE_NO_CHECK): New macro.
(FETCH_CHAR_ADVANCE): Check multibyteness of the current buffer.