_split_header(): Split on folding whitespace if the attempt to split
on semi-colons failed.
_split_header(): Patch by Matthew Cowles for fixing SF bug # 471918,
Generator splitting long headers.
_handle_text(): If the payload is None, then just return (i.e. don't
write anything). Subparts of message/delivery-status types
will have this property since they are just blocks of headers.
Also, when raising the TypeError, include the type of the
payload in the error message.
_handle_multipart(), _handle_message(): When creating a clone of self,
pass in our _mangle_from_ and maxheaderlen flags so the clone
has the same behavior.
_handle_message_delivery_status(): New method to do the proper
printing of message/delivery-status type messages. These have
to be handled differently than other message/* types because
their payloads are subparts containing just blocks of headers.
In class DecodedGenerator:
_dispatch(): Skip over multipart/* messages since we don't care
about them, and don't want the non-text format to appear in
the printed results.
<http://sf.net/projects/mimelib>. There /are/ API differences between
mimelib and email, but most of the implementations are shared (except
where cool Py2.2 stuff like generators are used).