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)

- Remove a bogus test: setsockopt() doesn't return a length, getsockopt()
does.
- Use %z to printf a size_t to fix compile on 64-bit platforms.

o setsockopt(2) cannot remove accept filter. [1]
o getsockopt(SO_ACCEPTFILTER) always returns success on listen socket
even we didn't install accept filter on the socket.
o Fix these bugs and add regression tests for them.

Submitted by: Igor Sysoev [1]
Reviewed by: alfred
MFC after: 2 weeks

Start the dreaded NOFOO -> NO_FOO conversion.

OK'ed by: core

Switch over to a different, more flexible test output protocol that's
understood by Perl's Test::Harness module and prove(1) commands.

Update README to describe the new protocol. The work's broken down into
two main sets of changes.

First, update the existing test programs (shell scripts and C programs)
to produce output in the ok/not ok format, and to, where possible, also
produce a header describing the number of tests that are expected to be
run.

Second, provide the .t files that actually run the tests. In some cases
these are copies of, or very similar too, scripts that already existed.
I've kept the old scripts around so that it's possible to verify that
behaviour under this new system (in terms of whether or not a test fails)
is identical to the behaviour under the old system.

Add a TODO file.

For variables that are only checked with defined(), don't provide
any fake value.

Use errx() instead of fprintf()/exit() for conciseness.

Suggested by: ru (some time ago)

Simple attachment regression test to attach the "accf_data" accept
filter to an inet socket and check at various points during the socket
life cycle that the filter can or cannot be attached, and that once
attached that the right one is attached and that it can be queried.