fix http://community.sharpdevelop.net/forums/t/15618.aspx - do not dispose change watcher in ChangeMarkerMargin - it could be used by two different margins (in two synchronized text editors, for ex. split view)

src/AddIns/DisplayBindings/AvalonEdit.AddIn/Src/ChangeMarkerMargin.cs

@@ -39,7 +39,6 @@ namespace ICSharpCode.AvalonEdit.AddIn
 		{
 			if (!disposed) {
 				changeWatcher.ChangeOccurred -= ChangeOccurred;
-				changeWatcher.Dispose();
 				disposed = true;
 			}
 		}

src/AddIns/DisplayBindings/AvalonEdit.AddIn/Src/CodeEditor.cs

@@ -610,6 +610,8 @@ namespace ICSharpCode.AvalonEdit.AddIn
 			
 			if (errorPainter != null)
 				errorPainter.Dispose();
+			if (changeWatcher != null)
+				changeWatcher.Dispose();
 			this.Document = null;
 			DisposeTextEditor(primaryTextEditor);
 			if (secondaryTextEditor != null)