Merge tag 'android-6.0.0_r26' into HEAD

Android 6.0.0 release 26

* tag 'android-6.0.0_r26':
  Add pcm_get_poll_fd
  Export pcm_mmap_avail
  initialize pcm_config to zero

Change-Id: I5f1139095b87e178b51f9f346442d105b36af52a