Fix showtabline=2/0 redraw issue similar with #64

Author: splhack

src/MacVim/MMVimController.m

@@ -574,8 +574,10 @@ - (void)handleMessage:(int)msgid data:(NSData *)data
         [windowController updateTabsWithData:data];
     } else if (ShowTabBarMsgID == msgid) {
         [windowController showTabBar:YES];
+        [self sendMessage:BackingPropertiesChangedMsgID data:nil];
     } else if (HideTabBarMsgID == msgid) {
         [windowController showTabBar:NO];
+        [self sendMessage:BackingPropertiesChangedMsgID data:nil];
     } else if (SetTextDimensionsMsgID == msgid || LiveResizeMsgID == msgid ||
             SetTextDimensionsReplyMsgID == msgid) {
         const void *bytes = [data bytes];