Run socket splicing regressions tests.  The error directory contains
tests, that invoke the splicing system call with invalid arguments.
The tcp and udp framework run a client, and a server, and a relay.
Each test 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.  The perf directory contains a C
program that can compare copy and splice performance.

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