dict: Support large iterations by sending data in output stream flush callback. Fixes also a hang if a lot of changes were done during the iteration.
dict: Support large iterations by sending data in output stream flush callback.
Fixes also a hang if a lot of changes were done during the iteration.

--HG--
branch : HEAD

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