[Dovecot] imapdir still a configuration option?

I've been looking at moving an old IMAPdir-based solution to dovecot. I came across references that dovecot (to my pleasant surprise) added imapdir support in 1.1. However, in trying 2.0.13 (from an OpenBSD package) things start okay, but I see in the logs:

"Initialization failed: Initializing mail storage from mail_location setting failed: Unknown mail storage driver imapdir"

Poking around in the sources, I still see lots of references to imapdir, but see very little in the documentation.

Is IMAPdir still supported in 2.0.x (or even 2.1.x)? I'd prefer not to have to migrate users via renaming, especially since they like the IMAPdir layout for their own searching.

--Kurt