(message-posting-charset): defvar when compiling.

(message-posting-charset): defvar when compiling.
(ietf-drums, gnus-util): Don't require.
(rfc2047-header-encoding-alist): Add `address-mime' part.  Doc
fixes.
(rfc2047-charset-encoding-alist): Use B for iso-8859-7,
iso-8859-8.
(rfc2047-q-encoding-alist): Augment header list.
(rfc2047-encoding-type): New.
(rfc2047-dissect-region): Deleted.
(rfc2047-encode-region, rfc2047-encode):  Rewritten to take
account of rfc2047 rules with respect to rfc2822 tokens and to do
encoding in place rather than by passing strings.
(rfc2047-encode-message-header): Don't include header name field
in encoding.  Add `address-mime' case and bind
rfc2047-encoding-type for `mime' case.
(rfc2047-encode-string): Doc fix.
(rfc2047-encode): Use longer chunks for base64.
(rfc2047-fold-region): Insert single characters, not strings.
(rfc2047-encoded-word-regexp): Wrap in eval-and-compile.
(rfc2047-decode-region): Avoid consing regexp in loop.