Updated mediawiki/extensions
Project: mediawiki/extensions/Wikibase  6776101c50bba7d70c6ab767dacd149623850968

More extensive testing of Change classes.

This adds extensive tests cases for the different Change
classes. It takes special care to test the serialization
of different data structures that may be contained in
Change objects.

Change-Id: I55ec8d947ca2670b00b6e307c34cfc11c74b57f7