x11, lists/tagged: initial use/x11/xscreensaver

xscreensaver has more than its main package and the details
of what to get where might be confusing for some of us;
in particular, there are 2D and 3D hacks collections
(and some arches would rather prefer to avoid 3D for now),
desktop file sets aimed for MATE/Xfce, and the frontend.

So let's provide some basic reusable targets.

features.in/x11/config.mk

@@ -2,6 +2,7 @@
 +icewm: use/x11/icewm; @:
 +xmonad: use/x11/xmonad; @:
 +nm-gtk: use/x11/gtk/nm; @:
++screensaver: use/x11/xscreensaver/gl; @:
 
 ## hardware support
 # the very minimal driver set
@@ -192,3 +193,13 @@ use/x11/leechcraft: use/x11
 
 use/x11/kde5: use/x11/xorg use/x11/kde/synaptic
 	@$(call add,THE_PACKAGES,kde5-big)
+
+## screensavers
+use/x11/xscreensaver:
+	@$(call add,THE_LISTS,$(call tags,base xscreensaver))
+
+use/x11/xscreensaver/gl: use/x11/xscreensaver
+	@$(call add,THE_LISTS,$(call tags,desktop xscreensaver))
+
+use/x11/xscreensaver/frontend: use/x11/xscreensaver
+	@$(call add,THE_PACKAGES,xscreensaver-frontend)

pkg.in/lists/tagged/base+xscreensaver

@@ -0,0 +1,3 @@
+xscreensaver
+xscreensaver-modules
+desktop-screensaver-modules-xscreensaver

pkg.in/lists/tagged/desktop+xscreensaver

@@ -0,0 +1,3 @@
+xscreensaver-hacks-rss_glx
+xscreensaver-modules-gl
+desktop-screensaver-modules-xscreensaver-gl