Changed EngineObject interface to use a common in/out buffer.
This clarifies code in the implemeting objects. It was a cause of bug,
fixes now in EngineVinylSoundEmu and EngineFilterBlock.
Merge remote-tracking branch 'upstream/master' into process_in_out

Conflicts:
	src/engine/enginemaster.cpp
fix fabs macro
add warning about fabs hotfix
Merge pull request #240 from daschuer/process_in_out

Changed EngineObject interface to use a common in/out buffer.