>>raverb+(OP)
Not sure why this was downvoted, 3.3 was when they started re-adding things that were removed in 3.0, to make supporting both 2 and 3 reasonable for libraries. I think it kept going in both 3.4 and 3.5 with more features, but the 3.3 restoration of the "u" string prefix is the one that I remember.