gtk2 rbgdkcursor.c: drop GTK_CHECK_VERSION(2,4,0)
gtk2 rbgdkwindow.c: drop GTK_CHECK_VERSION(2,4,0)
gtk2 rbgdkdraw.c: drop GTK_CHECK_VERSION(2,4,0)
gtk2 rbgdkscreen.c: drop GTK_CHECK_VERSION(2,4,0)
gtk2 rbgdkdisplay.c: drop GTK_CHECK_VERSION(2,4,0)
gtk3: add a test for Gtk::CssProvider
gtk3: remove a test for Gtk::RcStyle because it is deprecated
gtk3: add a test for Gtk::StyleContext
gtksourceview3: fix a typo in requirements version

3.0.0 or later ->
3.4.2 or later
  ^ ^
gtk3: use suitable name for title bar

CssAccordion ->
CSS Accordion
gtk3: use correct condition
Merge pull request #185 from cosmo0920/drop-gtk2.4.0-macro-gdk-part

drop GTK_CHECK_VERSION(2,4,0) macro in gtk2/rbgdk*.c

Patch by cosmo. Thanks!!!
gtk2: indent
gtk2: indent
gtk2: remove a trailing space
gtk2: fix unbaranced #endif