* rfc2047.el (rfc2047-encode-region): Check carefully whether to encode special

* rfc2047.el (rfc2047-encode-region): Check carefully whether to encode special
 characters;
 fix some kind of misconfigured headers;
 signal a real error if debug-on-quit or debug-on-error is non-nil.
(rfc2047-encode-max-chars): New variable.
(rfc2047-encode-1): Use it.
(rfc2047-encode-parameter): New function.

* mml.el (mml-insert-parameter): Remove an excessive space.