PulseAudio: preserve audio format, fix some races, simplify and cleanup
PulseAudio: preserve audio format, fix some races, simplify and cleanup

 - preserve sample format from VLC, if possible,
 - preserve physical channels mapping,
 - remove a useless callback,
 - fix small race conditions with pa_*_wait() on startup,
 - cosmetic changes.

krichter722/vlc,shyamalschandra/vlc,krichter722/vlc,vlc-mirror/vlc-2.1,jomanmuk/vlc-2.2,vlc-mirror/vlc-2.1,xkfz007/vlc,jomanmuk/vlc-2.2,vlc-mirror/vlc-2.1,xkfz007/vlc,vlc-mirror/vlc,vlc-mirror/vlc,krichter722/vlc,shyamalschandra/vlc,jomanmuk/vlc-2.1,vlc-mirror/vlc,vlc-mirror/vlc-2.1,vlc-mirror/vlc,jomanmuk/vlc-2.1,jomanmuk/vlc-2.1,jomanmuk/vlc-2.2,krichter722/vlc,vlc-mirror/vlc-2.1,jomanmuk/vlc-2.1,jomanmuk/vlc-2.2,vlc-mirror/vlc-2.1,jomanmuk/vlc-2.1,shyamalschandra/vlc,jomanmuk/vlc-2.1,shyamalschandra/vlc,krichter722/vlc,vlc-mirror/vlc,jomanmuk/vlc-2.1,xkfz007/vlc,shyamalschandra/vlc,vlc-mirror/vlc,krichter722/vlc,shyamalschandra/vlc,shyamalschandra/vlc,vlc-mirror/vlc-2.1,jomanmuk/vlc-2.2,xkfz007/vlc,xkfz007/vlc,vlc-mirror/vlc,xkfz007/vlc,jomanmuk/vlc-2.2,krichter722/vlc,jomanmuk/vlc-2.2,xkfz007/vlc