gnu/packages/gnome.scm (evolution-data-server)[outputs]: Add
'libedataserverui'.
[arguments]: Add phases so that only libedataserverui is linked with
WebKitGTK, and that it is moved to its own output.
(evolution, gnome-calendar, gnome-todo)[inputs]: Add libedataserverui.
Signed-off-by: Ludovic Courtès <ludo@gnu.org>