Run relayd regressions tests.  The framework runs a client, and a
server, and a relayd.  Currently the tcp and http forwarding code
path is covered.  Each test creates a special relayd.conf and starts
those three processes.  All processes write log files that are
checked for certain messages.  The test arguments are kept in the
args-*.pl files.  To find socket splicing bugs, each test is run
in both copy and splice mode.

SUDO=doas
As relayd needs root privileges either run the tests as root or set
this variable and run make as a regular user.  Only the code that
requires it, is run as root.

KTRACE=ktrace
Set this variable if you want a ktrace output from relayd.  Note that
ktrace is invoked after sudo as sudo would disable it.

RELAYD=/usr/src/usr.sbin/relayd/obj/relayd
Start an alternative relayd program that is not in the path.

LOCAL_ADDR, REMOTE_ADDR, REMOTE_SSH
Set these to run the relayd on a remote machine.  As the client and
server run locally, network timing may influence the test results.

Changes here have to be discussed with bluhm@, reyk@ or benno@.