* src/cryptcontroller.cpp (CryptController::update_mail_mapi):
Do actual update.
(create_encrypt_attach): Helper to set up the right attachment.
(write_data): Helper to write GpgME::Data to a sink.
* src/mail.cpp (Mail::update_crypt_mapi): Call update_mail_mapi.
* src/mimemaker.cpp, src/mimemaker.h: Export some more helpers.