Merge changes made in Gnus trunk.

Merge changes made in Gnus trunk.

message.texi (Insertion Variables): Document message-cite-style.
nnimap.el (nnimap-open-connection-1): Allow `network-only', too.
gssapi.el: New file separated out from imap.el to provide a general Kerberos 5 connection facility for Emacs.
message.el (message-elide-ellipsis): Document the format spec ellipsis.
message.el (message-elide-region): Allow the ellipsis to say how many lines were removed.
gnus-win.el (gnus-configure-frame): Protect against trying to restore window configurations containing buffers that are now dead.
nnimap.el (nnimap-parse-flags): Remove all MODSEQ entries before parsing to avoid integer overflows.
 (nnimap-parse-flags): Simplify the last change.
 (nnimap-parse-flags): Store HIGHESTMODSEQ as a string, since it may be too large for 32-bit Emacsen.
gnus-art.el (gnus-article-treat-body-boundary): Fix boundary width on XEmacs, which was one character too wide.
gnus-sum.el (gnus-articles-to-read): Use gnus-large-newsgroup as default number of articles to display.
 (gnus-articles-to-read): Use pretty names for prompt.
gnus-int.el (gnus-open-server): Ditto.
gnus-start.el (gnus-activate-group): Give a backtrace if debug-on-quit is set and the user hits `C-g'.
 (gnus-read-active-file): Ditto.
gnus-group.el (gnus-group-read-ephemeral-group): Ditto.