gtk2 rbgtkmenu.c: drop GTK_CHECK_VERSION(2,4,0)
gtk2 rbgtkbutton.c: drop GTK_CHECK_VERSION(2,4,0)
gtk2 rbgtkradioaction.c: drop GTK_CHECK_VERSION(2,4,0)
gtk2 rbgtkdrag.c: drop GTK_CHECK_VERSION(2,4,0)