When disabling keylock, explicitly reset musical pitch.
Also reset pitch when a new track is loaded.

Fixes lp#1361355
Merge branch 'master' into pitch_knob_stuck

Conflicts:
	src/engine/enginebuffer.cpp
	src/engine/enginebuffer.h
Merge branch 'master' into pitch_knob_stuck
Add tests for musical pitch reset.
cruft debug comment
Merge pull request #324 from ywwg/pitch_knob_stuck

When disabling keylock, explicitly reset musical pitch.