(ietf-drums): Don't require.

(ietf-drums): Don't require.
(message-posting-charset): defvar when compiling.
(rfc2047-header-encoding-alist): Add `address-mime' part.
(rfc2047-charset-encoding-alist): Use B for iso-8859-7,
iso-8859-8.  Doc fix.
(rfc2047-q-encoding-alist): Augment header list.
(rfc2047-encoding-type, rfc2047-syntax-table): New.
(rfc2047-encode-message-header): Account for address-mime method.
(rfc2047-dissect-region): Rewritten for RFC2822 rules.  Now just
return list of strings.
(rfc2047-encode-region): Change test for need to encode word.
Change rfc2047-encode call.
(rfc2047-encode): Remove CHARSET arg and decide encoding from
region contents.