* gnus.el (gnus-agent-covered-methods): Documented use of

	* gnus.el (gnus-agent-covered-methods): Documented use of
	named servers, not methods, to identity agentized groups.
	Users may now change their server configurations without having
	the server become "unagentized".
	(gnus-agent-covered-methods): Removed from gnus-variable-list to
	avoid storing two copies of gnus-agent-covered-methods, one in
	.newsrc.eld and the other in agent/lib/servers.
	(gnus-server-to-method): Do not cache server for the nil method.
	(gnus-method-to-server): New function.  Associate named server
	with all, even foreign, methods.
	(gnus-agent-method-p, gnus-agent-method-p-cache): Incorporated
	simple last-response cache to offset performance lose of having to
	always convert methods to named servers.