* rfc2047.el (rfc2047-encode-function-alist): Renamed from

* rfc2047.el (rfc2047-encode-function-alist): Renamed from
 `rfc2047-encoding-function-alist' in order to avoid conflicting with the old
  version.
(rfc2047-encode-region): Concatenate words containing non-ASCII characters in
 structured fields;
 don't encode space-delimited ASCII words even in unstructured fields;
 don't break words at char-category boundaries.
(rfc2047-encode-1): New function.
(rfc2047-encode): Use it;
 encode text so that it occupies the maximum width within 76-column;
 work correctly on Q encoding for iso-2022-* charsets.
(rfc2047-fold-region): Use existing whitespace for LWSP;
 make it sure not to break a line just after the header name.
(rfc2047-b-encode-region): Removed.
(rfc2047-b-encode-string): New function.
(rfc2047-q-encode-region): Removed.
(rfc2047-q-encode-string): New function.

* mm-util.el (mm-replace-in-string): New function.