kscreensaver-xsavers depends on xscreensaver-data not xscreensaver
build-dep on xscreensaver-data
add package kscreensaver-xsavers-extra with screensavers from xscreensaver-data-extra and xscreensaver-gl-extra
-webcollage depends on -extra not just xsavers
  * Edit kscreensaver-xsaver-webcollage.install to use the file
    from sources, since it does not get installed during build.

