Experiment with RubberBandStretcher::OptionWindowShort in PitchShiftEffect to reduce output latency

[Swiftb0y]

See RubberBandStretcher::Option. A shorter FFT window option will reduce the latency of the effect. We should do a bunch of tests to determine whether its worth the tradeoff in sound quality. The same option seems to be present on RubberBandLiveShifter though its not clear from the documentation whether that should result in improved latency. Can you clarify @cannam? Thank you.

CC @davidchocholaty