Audio engine changes:

-Idle tick is now responsible for dispatching all pending sound sources, as such improves priority sorting.
-Added ui sound precache mechanisms (to fetch sounds without associated soundsources)
-Audio engine no logner available pre-login or upon disconnect, for simplicity.
-General cleanup to the audio engine/impl.
-Fixed some gAudiop calls that were lacking prerequisite null checks.
-Added 'isUpstreamOK' procuedure to LLAssetStorage to allow avoidance of making requests when there is no upstream host connection.

indra/newview/llviewerwindow.cpp

@@ -1425,7 +1425,7 @@ BOOL LLViewerWindow::handleActivate(LLWindow *window, BOOL activated)
 		}
 
 		// Unmute audio
-		audio_update_volume();
+		audio_update_volume(false);
 	}
 	else
 	{
@@ -1450,7 +1450,7 @@ BOOL LLViewerWindow::handleActivate(LLWindow *window, BOOL activated)
 			stopGL();
 		}
 		// Mute audio
-		audio_update_volume();
+		audio_update_volume(false);
 	}
 	return TRUE;
 }