lib-storage: Include mail-index.h from mail-storage.h This makes it a bit more acceptable to use mail-index.h API, without having to go through the lib-storage layer. This is also needed by the next patch to avoid duplicating the same enum in both lib-index and lib-storage layer.

Added support for IMAP URLAUTH and URLAUTH=BINARY extensions Extends imap service with URLAUTH and URLAUTH=BINARY support: - Adds new commands URLFETCH, GENURLAUTH and RESETKEY. Creates imap-urlauth service in src/imap-urlauth. Functionality common to both the imap and imap-urlauth services is located in src/lib-imap-urlauth. TODO: - use mailbox GUIDs instead of names - doveadm command to delete stale urlauth entries? - add delay when attempting to access nonexistent user - create urlauth-worker queue, similar to how indexer-worker works (could we share code?..)