There are a number of steps that you can take to prepare your GTK+ 2.x
    application for the switch to GTK+ 3.
  
    Make sure your program only include the toplevel headers:
    
    make CFLAGS+="-DG_DISABLE_SINGLE_INCLUDES -DGDK_PIXBUF_DISABLE_SINGLE_INCLUDES -DGTK_DISABLE_SINGLE_INCLUDES"