gtk2: remove trailing spaces
gtk2: use "ifdef" instead of "if defined"

Because "ifdef" is used in other locations.
gdk3: add tests for Gdk::Event
gtk2 rbgtkcellrendererspin.c: drop GTK_CHECK_VERSION(2,10,0)
gtk2 rbgtkrecentmanager.c: drop GTK_CHECK_VERSION(2,10,0)
gtk2 rbgtkdrag.c: drop GTK_CHECK_VERSION(2,10,0)
gtk2 rbgtkstock.c: drop GTK_CHECK_VERSION(2,10,0)
gtk2 rbgtkpapersize.c: drop GTK_CHECK_VERSION(2,10,0)
gtk2 rbgtkprintoperation.c: drop GTK_CHECK_VERSION(2,10,0)
gtk2 rbgtklinkbutton.c: drop GTK_CHECK_VERSION(2,10,0)
gtk2 rbgtksizegroup.c: drop GTK_CHECK_VERSION(2,10,0)
gtk2 rbgtkselectiondata.c: drop GTK_CHECK_VERSION(2,10,0)
gtk2 rbgtkprintoperationpreview.c: drop GTK_CHECK_VERSION(2,10,0)
gtk2 rbgtktreeview.c: drop GTK_CHECK_VERSION(2,10,0)
gtk2 rbgtkrecentchooser.c: drop GTK_CHECK_VERSION(2,10,0)
gtk2 rbgtkcellrendereraccel.c: drop GTK_CHECK_VERSION(2,10,0)
gtk2 rbgtkstatusicon.c: drop GTK_CHECK_VERSION(2,10,0)
gtk2 rbgtktreestore.c: drop GTK_CHECK_VERSION(2,10,0)
gtk2 rbgtkpagesetup.c: drop GTK_CHECK_VERSION(2,10,0)
gtk2 rbgtkstyle.c: drop GTK_CHECK_VERSION(2,10,0)