When an envelope is scheduled for removal or expire, count it as
inflight. The queue sends an ack when it can actually process it.
The max inflight mechanism ensures that the scheduler never sends
envelopes faster than the queue can process.
Merge branch 'master' of ssh.poolp.org:/git/opensmtpd
Merge branch 'master' into portable
master uses reallocarray() but it was introduced after OpenBSD 5.5
preventing build of OpenSMTPD -master on OpenBSD -stable.

introduce reallocarray.c and conditionally build it if we detect
the system doesn't provide it
move queue_python to the OpenSMTPD-extras repository
add the no_chroot/chroot/user functions to the scheduler api.
fix scheduler_python
Merge branch 'master' of ssh.poolp.org:/git/opensmtpd
Merge branch 'master' into portable
move filter-python to OpenSMTPD-extras
Merge branch 'master' of ssh://ssh.poolp.org/git/opensmtpd
table_mysql moves to OpenSMTPD-extras
fix build
move table-ldap out of smtpd to OpenSMTPD-extras
move table_postgres to OpenSMTPD-extras
you're no longer welcome here
remove scheduler-python and scheduler-stub
remove scheduler-ram
table-redis and table-socketmap are moved to OpenSMTPD-extras
Merge branch 'master' of ssh://ssh.poolp.org/git/opensmtpd
no more backends in OpenSMTPD
remove filters