Hi!

I've added support for "IMAP4 Extension to SEARCH Command for Controlling
What Kind of Information Is Returned". It allows Gnus to uses some nice
features like very fast searching of minuid/maxuid or retrieving results
for SEARCH command in sequence-set. Also patch automatically routes query
from imap-search routine to the new imap-esearch when possible, as it
significantly reduces amount of consumed traffic.

Patch was tested with Zimbra server and it works well so far.