The event functions got renamed in obs.

We use the default format to avoid any resampling by pulse audio,
since obs will probably resample anyways if necessary.

pulse audio provides it's own convenience function to
iterate the mainloop, no need to use a custom one.
pulseaudio provides timing information for the stream, we use
that instead of system time.

Instead of copying the data from pulse to a local buffer and
then push it to obs, the pointer from pulse is now used and
pa_stream_drop() called afterwards.

- first try at implementing a pulse audio input plugin,
  it is currently completely untested.

- added license headers to source files