b=923106 recompute frequency dependent parameters when OscillatorType changes r=padenot

mSquare, mTriangle, and mSaw are not initialized in the OscillatorNodeEngine
constructor, just like they are not initialized when switching to
OscillatorType::Sine.  These parameters are initialized if and when switching
to the OscillatorTypes that use them.

mFinalFrequency, mNumberOfHarmonics, mSignalPeriod, mAmplitudeAtZero,
mPhaseIncrement, mPhaseWrap are not initialized in the OscillatorNodeEngine
constructor, just like they are not initialized immediately on switching
OscillatorType.  These parameters are initialized in
UpdateParametersIfNeeded(), conditional on mRecomputeParameters.

--HG--
extra : transplant_source : a%C1%83%03%03%5CJ%88%99j%A0%93%05%92%06%CA%D6%8B%00%21