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_openal.cpp

@@ -338,6 +338,7 @@ void LLAudioBufferOpenAL::cleanup()
 			LL_WARNS("OpenAL") << "Error: " << alutGetErrorString( error ) << " when cleaning up a buffer" << LL_ENDL;
 		}
 		mALBuffer = AL_NONE;
+		mLastSamplePos = 0;
 	}
 }