* gnus.texi (Gnus Unplugged): Refer to new agent Group/Topic

	* gnus.texi (Gnus Unplugged): Refer to new agent Group/Topic
	parameters.
	(Category Syntax): New description.
	(Category Buffer): New command.
	(Category Variables): New variables.
	(Agent as Cache): Expanded description.
	(Agent Expiry): Expanded description.
	(Agent Variables): Fixed and new descriptions.

        * infohack.el (batch-makeinfo): Provide local implementation of
	subst-char-in-region as the built-in implementation is unreliable
	on Windows XP (Intermittent failure results in build looping
	forever).