MAPI look into tnef attachments to detect protocol
* src/mapihelp.cpp (mapi_get_first_attach_data): New. (change_message_class_ipm_note_smime): Remove ms-tnef handling. Add multipart/signed protocol support for smime. Warn if encrypted fallback is used. (change_message_class_ipm_note_smime_multipartsigned): Remove ms-tnef handling. (parse_header_data): New helper factored out form (mapi_get_message_content_type): Handle ms-tnef wrapping.
If we have a mail with content-type ms-tnef we now
look into the tnef attachment to parse the protocol
While Outlook makes the original content type available
through API (get_first_attach_mime_tag) it does not
provide the protocol.
As we need this information early on for display purposes
we now look into the attachment.
- GnuPG-Bug-Id: T4267