Log Message:
Changes 2.24.0:
New API in gtkmm 2.24:
Gtk:
* ComboBox and ComboBoxText now have a has-entry property, so
  ComboBoxEntry and ComboBoxEntryText are deprecated.
* Range: Added get/set_round_digits()
Gdk:
* DragContext: Added drag_begin().
* Window: Added get_visual(), get_screen() and get_display().