(ONE_MORE_BYTE, TWO_MORE_BYTES): Set coding->resutl to

(ONE_MORE_BYTE, TWO_MORE_BYTES): Set coding->resutl to
CODING_FINISH_INSUFFICIENT_SRC if there's not enough source.
(ONE_MORE_CHAR, EMIT_CHAR, EMIT_ONE_BYTE, EMIT_TWO_BYTE,
EMIT_BYTES): New macros.
(THREE_MORE_BYTES, DECODE_CHARACTER_ASCII,
DECODE_CHARACTER_DIMENSION1, DECODE_CHARACTER_DIMENSION2): These
macros deleted.
(CHECK_CODE_RANGE_A0_FF): This macro deleted.
(detect_coding_emacs_mule): Use UNIBYTE_STR_AS_MULTIBYTE_P to
check the validity of multibyte sequence.
(decode_coding_emacs_mule): New function.
(encode_coding_emacs_mule): New macro.
(detect_coding_iso2022): Use ONE_MORE_BYTE to fetch a byte from
the source.
(DECODE_ISO_CHARACTER): Just return a character code.
(DECODE_COMPOSITION_START): Set coding->result instead of result.
(decode_coding_iso2022, decode_coding_sjis_big5, decode_eol): Use
EMIT_CHAR to produced decoded characters.  Exit the loop only by
macros ONE_MORE_BYTE or EMIT_CHAR.  Don't handle the case of last
block here.
(ENCODE_ISO_CHARACTER): Don't translate character here.  Produce
only position codes for an invalid character.
(encode_designation_at_bol): Return new destination pointer.  5th
arg DSTP is changed to DST.
(encode_coding_iso2022, decode_coding_sjis_big5): Get a character
from the source by ONE_MORE_CHAR.  Don't handle the case of last
block here.
(DECODE_SJIS_BIG5_CHARACTER, ENCODE_SJIS_BIG5_CHARACTER): These
macros deleted.
(detect_coding_sjis, detect_coding_big5, detect_coding_utf_8,
detect_coding_utf_16, detect_coding_ccl): Use ONE_MORE_BYTE and
TWO_MORE_BYTES to fetch a byte from the source.
(encode_eol): Pay attention to coding->src_multibyte.
(detect_coding, detect_eol): Preserve members src_multibyte and
dst_multibyte.
(DECODING_BUFFER_MAG): Return 2 even for coding_type_raw_text.
(encoding_buffer_size): Set magnification to 3 for all coding
systems that require encoding.
(ccl_coding_driver): For decoding, be sure that the result is
valid multibyte sequence.
(decode_coding): Initialize coding->errors and coding->result.
For emacs-mule, call decode_coding_emacs_mule.  For no-conversion
and raw-text, always call decode_eol.  Handle the case of last
block here.  If not coding->dst_multibyte, convert the resulting
sequence to unibyte.
(encode_coding): Initialize coding->errors and coding->result.
For emacs-mule, call encode_coding_emacs_mule.  For no-conversion
and raw-text, always call encode_eol.  Handle the case of last
block here.
(shrink_decoding_region, shrink_encoding_region): Detect cases
that we can't skip data more rigidly.
(code_convert_region): Setup src_multibyte and dst_multibyte
members of coding.  For decoding, if the buffer is multibyte,
convert the source sequence to unibyte in advance.  For encoding,
if the buffer is multibyte, convert the resulting sequence to
multibyte afterward.
(run_pre_post_conversion_on_str): New function.
(code_convert_string): Deleted and divided into the following two.
(decode_coding_string, encode_coding_string): New functions.
(code_convert_string1, code_convert_string_norecord): Call one of
above.
(Fdecode_sjis_char, Fdecode_big5_char): Use MAKE_CHAR instead of
MAKE_NON_ASCII_CHAR.
(Fset_terminal_coding_system_internal,
Fset_safe_terminal_coding_system_internal): Setup src_multibyte
and dst_multibyte members.
(init_coding_once): Initialize iso_code_class with new enum
ISO_control_0 and ISO_control_1.