Updated mediawiki/extensions
Project: mediawiki/extensions/OpenSearchXml  4247abc00eb9612f674e67ab57e5728a285b62a0

Update for merge into core

Core change Ie0ab9090 merges the functionality of this extension into
core.

Add a README file about the deprecation, and add detection into
OpenSearchXml.php so the extension doesn't stomp on core.

Change-Id: I297e975a2887afb2154372bf029d669e07138746