Code slush for MediaWiki 1.13

I’m declaring a “code slush” on MediaWiki trunk for the next week or so, so we can concentrate on cleaning things up for making a 1.13 release branch, timed oh-so-delicately to approximately coincide with the Wikimania conference (coming up July 17-19).

I’d like to ask that new experimental features and giant refactorings that aren’t vital fixes be pushed back until after the branching; this’ll give us all a chance to make sure the release goes smoothly and that changes that are made get the attention they deserve.

It’s a-gonna be awesome! :D