* audio-port: small optimizations
* mixer: removed obsolete idle-property of worker-threads
* FX-mixer: protect individual buffers of FX-channels from being processed by more than one thread
git-svn-id: https://lmms.svn.sf.net/svnroot/lmms/trunk/lmms@979 0778d3d1-df1d-0410-868b-ea421aaaa00d