* gnus-agent.el (gnus-agent-expire-days): Removed obsolete

	* gnus-agent.el (gnus-agent-expire-days): Removed obsolete
	documentation.
	(gnus-agentize, gnus-agent-add-server, gnus-agent-remove-server):
	Modified to support new definition of gnus-agent-covered-method.
	(gnus-agent-read-servers): Rewritten to convert old method data
	into server names.
	(gnus-agent-read-servers-validate)
	(gnus-agent-read-servers-validate-native): New functions.
	(gnus-agent-write-servers): No longer use gnus-method-simplify as
	it failed to simplify foreign methods.
	(gnus-agent-close-connections, gnus-agent-synchronize-flags)
	(gnus-agent-possibly-synchronize-flags, gnus-agent-fetch-session)
	(gnus-agent-regenerate): Uses new gnus-agent-covered-methods
	function as gnus-agent-covered-methods variable no longer provides
	methods.
	(gnus-agent-covered-methods): New function
	(gnus-agent-expire-group, gnus-agent-expire): Final message will,
	if gnus-verbose is greater than 4, report statistics of NOV
	entries and files deleted as well as total bytes recovered.
	(gnus-agent-expire-done-message): New function
	(gnus-agent-unread-articles): Bug fix.  No longer drops last
	unread article onto read list.
	(gnus-agent-regenerate-group): Changed prompt to use typical
	style.
	(gnus-agent-group-covered-p): Rewrote to internally use
	gnus-agent-method-p.