[IPLUG/VST2/VST3/AU] added void IPlugBase::SetTailSize(unsigned int tailSizeSamples)

needed this for VST3 Endless Series because plugin was getting suspended when it should have been tone generating. useful for reverbs too i suppose
[IPLUG/WIN] simplify the #ifdefed GetMouseMod(WPARAM wParam) options for ALT key in ProTools