Updated mediawiki/extensions
Project: mediawiki/extensions/Wikibase  5ebe8a65ffd8b3849f309f3ee858ca719112df4e

Make wbclient.linkItem more user friendly

Changes:
1. The item the page links goes from is now linked when conforming
   page links
2. A meaningful error is shown at an early stage if the page the
   user wants to link to is already linked with an item having a link
   to a local page
3. Some minor improvements and removals of old temporary code

This breaks backwards compatiblity on the client but that doesn't
matter as all that isn't used in production anywhere yet.

Change-Id: I60278018d749d3bba0debb201d2df23fa9e5b9bc