Include composite.h.

Include composite.h.
(DECODE_CHARACTER_ASCII): Don't handle composition here.
(DECODE_CHARACTER_DIMENSION1): Likewise.  Don't check the validity
of multibyte code here.
(DECODE_CHARACTER_DIMENSION2): Likewise.
(detect_coding_emacs_mule): Change the case label from
EMACS_leading_code_composition to 0x80.
(detect_coding_iso2022): Handle new composition sequence.
(DECODE_ISO_CHARACTER): Likewise.
(check_composing_code): Deleted.
(coding_allocate_composition_data): New function.
(CODING_ADD_COMPOSITION_START) (CODING_ADD_COMPOSITION_END)
(CODING_ADD_COMPOSITION_COMPONENT) (DECODE_COMPOSITION_START)
(DECODE_COMPOSITION_END) (DECODE_COMPOSITION_RULE): New macros.
(decode_coding_iso2022): Handle new composition sequence.
(ENCODE_ISO_CHARACTER): Don't check composition here.
(ENCODE_COMPOSITION_RULE) (ENCODE_COMPOSITION_START): New macros.
(ENCODE_COMPOSITION_NO_RULE_START)
(ENCODE_COMPOSITION_WITH_RULE_START): Deleted.
(ENCODE_COMPOSITION_END): Handle new composition sequence.
(ENCODE_COMPOSITION_FAKE_START): New macro.
(encode_coding_iso2022): Handle new composition sequence.
(ENCODE_SJIS_BIG5_CHARACTER): Delete superfluous `;' at the tail.
(encode_coding_sjis_big5): Ignore composition.
(setup_coding_system): Initialize new members of struct
coding_system.  Enable composition only when the coding system has
`composition' property t.
(coding_free_composition_data) (coding_adjust_composition_offset)
(coding_save_composition) (coding_restore_composition): New
functions.
(code_convert_region): Call coding_save_composition for encoding
and coding_allocate_composition_data for decoding.  Don't skip
ASCII characters if we handle composition on encoding.  Call
signal_after_change with Check_BORDER.
(code_convert_string): Call coding_save_composition for encoding
and coding_allocate_composition_data for decoding.  Don't skip
ASCII characters if we handle composition on encoding.
(code_convert_string1): Set Vlast_coding_system_used after calling
code_convert_string.
(code_convert_string_norecord): Disable composition.
(Fset_terminal_coding_system_internal): Likewise.
(Fset_safe_terminal_coding_system_internal): Likewise.
(Fset_keyboard_coding_system_internal): Likewise.
(init_coding_once): Set emacs_code_class[0x80] to
EMACS_invalid_code.