evolution-data-server: fix build with libxml2-2.9.0

* newer eds versions depend on external libgdata
  http://git.gnome.org/browse/evolution-data-server/commit/servers?h=gnome-2-32&id=28897beab5dcd4aab3586322a96280be92585db6


  but for this one, we need this patch

Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>
Signed-off-by: Koen Kooi <koen@dominion.thruhere.net>