Sodium 0.5.0 is the bare minimum.
libevent2: Fix race caused by event_active
There is a race between manual event_active and natural event activation.

If both happen at the same time on the same FD, they would both be protected by the same event base lock except for 1 LoC where the fields of struct event are read without any kind of lock.

This commit does those reads into local variables inside the lock and then invokes the callback with those local arguments outside the lock.

In 2.0-stable, none of this is inside the lock; in HEAD, only the callback is read inside the lock. This gets the callback and all 3 arguments inside the lock before calling it outside the lock.
Use sodium 1.0.1
logger() -> logger_noformat()
Indent
A file descriptor doesn't have to be >= 0
Check for libsystemd-daemon in addition to libsystemd.
Do not pick systemd unless --with-systemd is explicitly used.
Outline systemd descriptors initialization
The TCP socket is of type SOCK_STREAM.
Add SYSTEMD_DAEMON_ flags
Add a simple sample systemd service file.
Fix error message
UDP sent by systemd sockets are not listening
When using systemd, the local address may not reflect the reality.