* gnus-agent.el (gnus-agent-read-agentview): Removed support for

	* gnus-agent.el (gnus-agent-read-agentview): Removed support for
	old file versions.
	(gnus-group-prepare-hook): Removed function that converted list
	form of gnus-agent-expire-days to group properties.

	* gnus-int.el: Autoload gnus-agent-regenerate-group.
	(gnus-request-accept-article): Re-indented.

	* gnus-start.el (gnus-convert-old-newsrc): Registered new
	converters to handle old agent file formats.  Added logic for a
	"backup before upgrading warning".
	(gnus-convert-mark-converter-prompt): Developers can mark
	functions as needing (default), or not needing,
	gnus-convert-old-newsrc's "backup before upgrading warning".
	(gnus-convert-converter-needs-prompt): Tests whether the user
	should be protected from potentially irreversable changes by the
	function.

	* legacy-gnus-agent.el (): New. Provides converters that are only
	loaded when gnus-convert-old-newsrc needs to call them.