gnome-base/libgnomekbd: Add missing gtk+ USE=X dependency

libgnomekbd uses gdkx directly and relies on Xorg for its functionality still for now.

Gentoo-bug: 599664
Package-Manager: Portage-2.3.4, Repoman-2.3.1

gnome-base/libgnomekbd/libgnomekbd-3.22.0.1.ebuild

@@ -1,4 +1,4 @@
-# Copyright 1999-2016 Gentoo Foundation
+# Copyright 1999-2017 Gentoo Foundation
 # Distributed under the terms of the GNU General Public License v2
 
 EAPI=6
@@ -15,7 +15,7 @@ IUSE="+introspection test"
 
 RDEPEND="
 	>=dev-libs/glib-2.18:2
-	>=x11-libs/gtk+-2.91.7:3[introspection?]
+	>=x11-libs/gtk+-2.91.7:3[X,introspection?]
 	>=x11-libs/libxklavier-5.2[introspection?]
 
 	introspection? ( >=dev-libs/gobject-introspection-0.6.7:= )