gtk2 rbgdkwindow.c: drop GTK_CHECK_VERSION(2,10,0)
gtk2 rbgtkselection.c: drop GTK_CHECK_VERSION(2,10,0)
gtk2 rbgtkrecentchoosermenu.c: drop GTK_CHECK_VERSION(2,10,0)
gtk2 rbgtkrecentfilterinfo.c: drop GTK_CHECK_VERSION(2,10,0)
gtk2 rbgtkwindow.c: drop GTK_CHECK_VERSION(2,10,0)
gtk2 rbgtkrecentchooserwidget.c: drop GTK_CHECK_VERSION(2,10,0)
gtk2 rbgtkrecentinfo.c: drop GTK_CHECK_VERSION(2,10,0)
gtk2 rbgtkrecentfilter.c: drop GTK_CHECK_VERSION(2,10,0)
gtk2 rbgtkprintcontext.c: drop GTK_CHECK_VERSION(2,10,0)
gtk2 rbgtktargetlist.c: drop ! GTK_CHECK_VERSION(2,10,0)

Because of drop GTK+ < 2.10 support, it is unneeded.
gtk2 rbgtkradioaction.c: drop #if ! GTK_CHECK_VERSION(2,10,0)

Because of drop GTK+ < 2.10 support, it is unneeded.