maintaining.texi: Suopport fo Arch has been moved to obolte.

Remove references that imply otherwise.
Make gnutls-peer-status return even more data

* src/gnutls.c (Fgnutls_peer_status): Return the key exchange, cipher
and MAC algorithms.
* lisp/net/nsm.el (nsm-check-protocol): Test for RC4 on `high'.
Make the NSM prompting have more data

(nsm-format-certificate): Include more data about the connection.
(nsm-query): Fill the text to that it looks nicer.
Make NSM warn on `high' for older protocols, and document

* doc/emacs/misc.texi (Network Security): Mention the new protocol-level
`high' NSM checks.

(nsm-check-protocol): Also warn if using SSL3 or older.