(SAFE_ONE_MORE_BYTE): New macro.

(SAFE_ONE_MORE_BYTE): New macro.
(DECODE_EMACS_MULE_COMPOSITION_CHAR): New macro.
(DECODE_EMACS_MULE_COMPOSITION_RULE): New macro.
(decode_composition_emacs_mule): New function.
(decode_coding_emacs_mule): Decode composition sequence by calling
decode_composition_emacs_mule.
(ENCODE_COMPOSITION_EMACS_MULE): New macro.
(encode_coding_emacs_mule): Changed from macro to function.  If
a text contains compostions, encode them correctly.
(setup_coding_system): Set coding->commong_flags for emacs-mule so
that decoding and encoding are required.