Copy stable/9 to releng/9.3 as part of the 9.3-RELEASE cycle.

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

Copy head to stable/9 as part of 9.0-RELEASE release cycle.

Approved by: re (implicit)

Always assign WARNS using ?=

- fix some nearby style bugs
- include Makefile.inc where it makes sense and reduces duplication

Approved by: ed (co-mentor)

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.