add license header to fastlog.h
fix #17673: arpeggio playback
fix arpeggio default height
fix #17521: Replacing arpeggio and undo removes it completely
add ability to change arpeggio by drag/drop/dbl click
travis: try to kill Xvfb when tests fail
fix #20083: Fall/Doit modification causes unredable mscx file and crash