Implemented RenderOverlay hook that executes directly after level and statusbar

src/d_main.cpp

@@ -900,6 +900,8 @@ void D_Display ()
 	{
 		NetUpdate ();			// send out any new accumulation
 		// normal update
+		// draw ZScript UI stuff
+		E_RenderOverlay();
 		C_DrawConsole (hw2d);	// draw console
 		M_Drawer ();			// menu is drawn even on top of everything
 		FStat::PrintStat ();