create a 6.x release

I believe that HEAD is 6.x compatible. Can you branch it and create a 6.x-dev release?

Just 5 minutes ago in IRC someone said "I was sad to see that simpletest isn't ported to 6.x. I was thinking of writing my own testing framework since simpletest seems abandoned."

Obviously that was a misinformed view, but whatever we can do to prevent that from happening seems worthwhile.