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

dscho/dovecot,dscho/dovecot,dscho/dovecot,dscho/dovecot,dscho/dovecot