clean out all diffs that are not master_sync
Address notes.
Merge remote-tracking branch 'localywwg/formerge' into master_sync

Conflicts:
	mixxx/src/engine/bpmcontrol.cpp
	mixxx/src/engine/bpmcontrol.h
	mixxx/src/engine/enginebuffer.cpp
	mixxx/src/engine/enginebuffer.h
	mixxx/src/engine/enginechannel.cpp
	mixxx/src/engine/enginemaster.cpp
	mixxx/src/engine/enginesync.cpp
	mixxx/src/engine/enginesync.h
	mixxx/src/engine/ratecontrol.cpp
	mixxx/src/engine/ratecontrol.h
Fix build
Address notes.