* lily/my-lily-lexer.cc (prepare_for_next_token): use previous

* lily/my-lily-lexer.cc (prepare_for_next_token): use previous
token for origin information.

* lily/parser.yy (My_lily_lexer): do identifier location and
cloning from lexer.

* scm/music-functions.scm (make-multi-measure-rest): move mmrest
logic out of the parser.

* Documentation/user/refman.itely (Multi measure rests): add more
notes about mm rests.