Fix processing of netbeans messages

Processing of netbeans messages in macvim has been broken since
1e08012 due to that
processing being moved to gui_x11.c. Add similar block to gui_macvim.m
to restore the processing of netbeans messages.

Author: ervandew

src/MacVim/gui_macvim.m

@@ -392,6 +392,11 @@
     // called, so force a flush of the command queue here.
     [[MMBackend sharedInstance] flushQueue:YES];
 
+#if defined(FEAT_NETBEANS_INTG)
+    /* Process any queued netbeans messages. */
+    netbeans_parse_messages();
+#endif
+
     return [[MMBackend sharedInstance] waitForInput:wtime];
 }