add mta_connector
Merge branch 'master' into mta-delay

Conflicts:
	smtpd/mta.c
simplify mta_drain() a bit
do not take a unnecessary ref on relay in mta_drain()
Better comments
small tweaks
refine the mta connection handling logic
Add functions for composing and parsing imsg safely
fix enum comparison warning
handle reconnection delay on connector
Merge branch 'master' into mta-delay
Merge branch 'master' into msg
implement typed message formating functions
remove queue_data_msg and use a typed message instead.
use typed messages for mfa data, and requests.
use typed messages for queue
use mproc for filter implementation.
use typed messages for mfa and filters.
simplify swicth
change lka to use typed msg.
use typed messages for dns queries