* lily/parser.yy (command_element): move clef stuff into Scheme.

* lily/parser.yy (command_element): move clef stuff into Scheme.

* lily/part-combine-music.cc: removed file and class.

* lily/context-specced-music-iterator.cc (class
Context_specced_music_iterator): new file. Obsoletes the
Context_specced_music type.

* scm/music-types.scm (make-repeated-music): put different kinds
of repeated music into music-type table.

* lily/include/command-request.hh: removed
lily/include/musical-request.hh: removed. Removed all _req classes
except Key_change_req. Changes throughout.