(GLYPH): Change type from int to struct with separate char

(GLYPH): Change type from int to struct with separate char
and face_id members.
(GLYPH_MASK_FACE, GLYPH_MASK_CHAR): Delete macros.
(GLYPH_CHAR, GLYPH_FACE): Remove slow versions with frame arg.
(FAST_GLYPH_CHAR, FAST_GLYPH_FACE): Rename macros to ...
(GLYPH_CHAR, GLYPH_FACE): ... these.  Change users.
(FAST_MAKE_GLYPH, MAKE_GLYPH): Remove.  Rewrite users to use ...
(SET_GLYPH, SET_GLYPH_CHAR, SET_GLYPH_FACE): ... these macros instead.
(GLYPH_CODE_CHAR, GLYPH_CODE_FACE, GLYPH_CODE_P)
(GLYPH_CODE_CHAR_VALID_P, SET_GLYPH_FROM_GLYPH_CODE): New macros to
handle new Lisp glyph code encoding, either an integer or a cons.