21.5-b3: setting up default faces for gtk-xemacs

Rather than submit this to xemacs-patches immediately, I thought it would be prudent to post it here first. The problem is that an XEmacs 21.5-b3 built --with-gtk doesn't set up default faces (on my system). To reproduce, start xemacs -q -vanilla and highlight a region with the mouse; is it visible? There is code in gtk-faces.el (namely gtk-init-device-faces) to set the 'highlight' face to look like GTK_STATE_PRELIGHT and 'zmacs-region' like GTK_STATE_SELECTED but it precludes further customization via M-x customize-face or a custom-set-faces form, which is probably why it was effectively disabled by quoting its main let* form. faces.el makes some useful default faces, but the gtk defaults were commented out. So I uncommented the commented-out gtk defaults and added additional ones. -- John Paul Wallington