Made further refinements to the audioengine:

-Looping syncslaves are stopped when there is no syncmaster.
-Hardened against edge cases regarding soundsource priority sorting.
-Fixed issue with syncmasters being marked as having looped when instead they just started playing (caused double-start of syncslaves).
-Updated some comments.

indra/llaudio/llaudioengine_fmod.cpp

@@ -590,6 +590,7 @@ void LLAudioChannelFMOD::cleanup()
 	}
 
 	mChannelID = 0;
+	mLastSamplePos = 0;
 }