[Dovecot] Patch: 2.0 support for URLAUTH, BURL, CATENATE

Thank you Timo for beginning the port of URLAUTH, BURL, and CATENATE from 1.2 to 2.0. Attached please find two patches that finish the port to 2.0. One patch updates the dovecot-2.0-urlauth branch and is based on the tip of that branch. The other patch adds the full support to dovecot-2.0.beta5. The resulting URLAUTH/BURL/CATENATE code is the same.

Please let me know if you have any questions about these patches. Thanks.