Fix :transpose? #t, #:include-midi? #t produce bad audio playback

 Divided code from procedure ly-score:make-score between two
 procedures, ly-score:make-layout-score and ly-make-audio-score.
 These are called in sequence from where ly-score:make-score was
 called previously, producing a layout-only and midi-only version
 of the music. Both scores are added to the book if necessary.

Files changed:
	ly/ly-score.ly