- The buffer size is now set with set_buffer_size_near()
 - The size of the buffer is now independant of periods
 - snd_pcm_sw_params_set_avail_min() is now called with the previous
   power of 2 rather than the next.
 - The start threshold is now called with the previous power of 2
   rather than the next.

  - mal_device_get_available_rewind_amount()
  - mal_device_rewind()

ALSA: Address an issue where it was possible for some samples to get dropped when a capture device is closed.

Improve the DirectSound backend by not using notifications exclusively to manage data retrieval and submission.

 - Fix error with usleep() being undefined.
 - Add support for 64-bit floating point formats for ALSA.

Fix an issue with the DirectSound backend where there'd be some leftover samples that are not sent to the application when a capture device is stopped.

  - Use binary semaphores as the synchronization primitive for the worker thread
  - Generalize the worker thread so as to avoid having different worker thread
    for each backend.
  - Make state changes atomic

General improvements bug fixing:
  - Fix an error where the DirectSound backend would immediately send the
    application a bunch of invalid audio data.
  - Have the ALSA backend request more audio data only immediately before it's
    ready to write it to the device.
  - General improvements on documentation.
  - Update readme.