windows WASAPI fixes/improvements:

windows WASAPI fixes/improvements:
- fixed dependency of framesPerBuffer parameter in Pa_OpenStream and latency (now only latency setting affects device latency which is correct behavior);
- paFramesPerBufferUnspecified is now supported for Pa_OpenStream;
- sound distortion fixed for Shared mode if framesPerBuffer is lower than device limit and when latency was set to 0;
- fixed timeout for Exclusive mode due to buffer misalignment;
- improved precision of DAC/ADC time for running stream;
- avoided memory leaks on failure of Pa_OpenStream;
- NULL checks on stream pointer for all external methods;
- correct host buffer mode for paWinWasapiPolling mode to deliver fixed number of frames to user space;
- implemented workaround for Vista x64 WOW64 bug if Event-mode is used for Shared mode (due to incorrect Event signaling audio dropouts were happening): will fall back to safe Polling method automatically.