Take colors for region face (selected text) from the Gtk+ theme.

Take colors for region face (selected text) from the Gtk+ theme.

* lisp/dynamic-setting.el (dynamic-setting-handle-config-changed-event):
Handle theme-name change.

* lisp/faces.el (region): Add type gtk that uses gtk colors.

* src/gtkutil.c (xg_check_special_colors, style_changed_cb): New functions.
(xg_create_frame_widgets): Connect theme name changes to
style_changed_cb.

* src/gtkutil.h (xg_check_special_colors): Declare.

* src/xfns.c (x_defined_color): If USE_GTK, call xg_check_special_colors
first.