Change sampleCount arguments, variables, return values to size_t...

... whenever they really describe the size of a buffer that fits in memory, or
of a block file (which is never now more than a megabyte and so could be fit in
memory all at once), or a part thereof.

src/effects/NoiseRemoval.cpp

@@ -366,7 +366,7 @@ void EffectNoiseRemoval::StartNewTrack()
    mOutSampleCount = -(int)((mWindowSize / 2) * (mHistoryLen - 1));
 }
 
-void EffectNoiseRemoval::ProcessSamples(sampleCount len, float *buffer)
+void EffectNoiseRemoval::ProcessSamples(size_t len, float *buffer)
 {
    int i;