Merge changes made in Gnus trunk.

Merge changes made in Gnus trunk.

message.texi (Various Commands): Document format specs in the ellipsis.
time-date.el (format-seconds): Use assoc instead of assoc-string to avoid warning on XEmacs.
gnus-art.el: Require mouse, which the build bot seems to say is needed.
gravatar.el (gravatar-retrieve-synchronously): Use `url-retrieve' on XEmacs, since it doesn't have url-retrieve-synchronously.
time-date.el (format-seconds): Use assoc instead of assoc-string, since assoc-string doesn't exist in XEmacs.
gnus-group.el (gnus-group-list-ticked): New function.
 (gnus-group-make-menu-bar): Provide a menu entry for it.
 (gnus-group-list-map): Provide a binding for it.
shr.el (shr-visit-file): New command.
nnimap.el (nnimap-fetch-inbox): Rewrite slightly last patch.
nnimap.el (nnimap-fetch-inbox): Don't download bodies on ver4-capable servers.