Mute button + RT shows up immediately now in Windows Mixer

see issue 803

rtgui/options.h

@@ -143,6 +143,8 @@ class Options {
     Glib::ustring sndBatchQueueDone;
     Glib::ustring sndLngEditProcDone;
     double sndLngEditProcDoneSecs;  // Minimum processing time seconds till the sound is played
+    bool sndEnable;
+
     bool tunnelMetaData;  // Pass through IPTC and XMP unchanged
     int histogramPosition;  // 0=disabled, 1=left pane, 2=right pane
     bool showProfileSelector;