Fix text getting appended to vid_restart in command buffer

I was getting unknown command "vid_restart-button2" warning on OSX when trying to use alt-return to toggle fullscreen.

code/sdl/sdl_input.c

@@ -999,7 +999,7 @@ void IN_Frame( void )
 	if ( (vidRestartTime != 0) && (vidRestartTime < Sys_Milliseconds()) )
 	{
 		vidRestartTime = 0;
-		Cbuf_AddText( "vid_restart" );
+		Cbuf_AddText( "vid_restart\n" );
 	}
 }