Handle returning mixed header+body multiple times without breaking. Handle correctly callbacks excluding headers and seeking back and re-reading header.
Handle returning mixed header+body multiple times without breaking. Handle
correctly callbacks excluding headers and seeking back and re-reading header.

--HG--
branch : HEAD

jwm/dovecot-notmuch,jwm/dovecot-notmuch,jwm/dovecot-notmuch,jkerihuel/dovecot,jkerihuel/dovecot,jwm/dovecot-notmuch,jkerihuel/dovecot,jwm/dovecot-notmuch,jkerihuel/dovecot,jkerihuel/dovecot