macosx: do not animate change between dropzone and playlist

This would result in an unpleasant black or grey area for
a short time, for instance when selecting the media library.
macosx: add workaround to avoid grey or transparent top bars in fullscreen mode

close #9469
auhal: unlock mutex in stream listener error paths
auhal: do not check for changed streams if selected device is 0
auhal: remove unneeded global variable
auhal: check if render callback does not want data

Indeed this can happen rarely.
auhal: do an early check for the stream format set

This prevents waiting for the timeout in some situations, especially
if the format was already set to the new value before.
auhal: prevent revert to unusual formats after SPDIF playback

Getting the current format is unreliable, for instance if the audio
cable is plugged in while playback is running. Thus only the
first original format is trusted.

close #9957