Regtests for 2.15.3

[Phil Holmes]

Official regtests: pretty clean.  Not sure about:

+warning: MIDI channel wrapped around
+warning: remapping modulo 16
warning: MIDI channel wrapped around
warning: remapping modulo 16
warning: MIDI channel wrapped around

in midi-volume-equaliser.log and

-warning: MIDI channel wrapped around
-warning: remapping modulo 16
Interpreting music...
Preprocessing graphical objects...

in midi-dynamics.log

Using my pixel comparator against 2.14.0, I see differences in multimeasure 
rest sizes for rests of 8, 9 and 10 measures - the bars are closer together. 
To my eyes better, but I would like a check that this is deliberate.

In note-line.ly and tuplet-bracket-cross-staff.ly I see beams on shorter 
stems - i.e. the beam is closer to the notehead.  Deliberate?

That's all.

--
Phil Holmes
Bug Squad