Copy head@r302406 to stable/11 as part of the 11.0-RELEASE cycle.
Prune svn:mergeinfo from the new branch, as nothing has been merged
here.

Additional commits post-branch will follow.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

Rework tcpp output so that it generates a comma-delimited list of values,
optionally with a header if "-h" is passed. Toast CPU time measurement
in the server for now. Remove -C and -T, since we now always report
both connections/sec and Gb/sec.

MFC after: 1 week
Sponsored by: Juniper Networks

Although we currently don't compile in CPU-pinning support by default,
add a -P to enable it if it were.

MFC after: 1 week
Sponsored by: Juniper Networks

Add tcpp -- TCP parallelism microbenchmark.

This tool creates large numbers of TCP connections, each of which will
transmit a fixed amount of data, between client and server hosts. tcpp can
use multiple workers (typically up to the number of hardware cores), and can
use multiple source IPs in order to use an expanded port/IP 4-tuple space to
avoid problems from reusing 4-tuples too quickly. Aggregate bandwidth use
will be reported after a client run.

While by no means a perfect tool, it has proven quite useful in generating
and optimizing TCP stack lock contention by easily generating high-intensity
workloads. It also proves surprisingly good at finding device driver bugs.