Implement new IMAP search feature, proposed by egh@e6h.org

Implement new IMAP search feature, proposed by egh@e6h.org

2011-07-17  David Maus  <dmaus@ictsoc.de>

	* elmo-util.el (elmo-list-difference): New function. Return
	difference of two lists.
	* elmo-imap4.el (elmo-imap4-search-generate-vector): Use function.

2011-07-03  Erik Hetzner  <egh@e6h.org>

	* elmo-imap4.el (elmo-imap4-search-internal-primitive): Removed.
	(elmo-imap4-search-build-full-command): New function. Build full
	IMAP search command.
	(elmo-imap4-search-perform): New function. Perform IMAP search.
	(elmo-imap4-search-generate-vector): New function. Generate search
	vector.
	(elmo-imap4-search-mergeable-p): New function. Return non-nil if
	two search conditions are mergeable.
	(elmo-imap4-search-mergeable-charset): New function. Return
	charset of two searches for merging.
	(elmo-imap4-search-generate-uid): New function. Return search for
	a set of messages.
	(elmo-imap4-search-generate-and): New function. Return search that
	returns intersection of two search commands.
	(elmo-imap4-search-generate-or): New function. Return search that
	returns union of two search commands.
	(elmo-imap4-search-generate): New function. Return search in
	folder.
	(elmo-imap4-search-internal): Use new search functions.