Detect a runtime error if the bytes argument is not as expected.

This is based on https://github.com/freebsd-net/packetdrill/pull/15
but adds support for af_arg, getsockopt() and clearing the
acceptfilter.

Allow the last parameter of setsockopt() and getsockopt() calls
to be ....

This was suggested in https://github.com/freebsd-net/packetdrill/pull/15
and a partial implementation was provided.

Sponsored by:	Netlix, Inc.

On FreeBSD IPv6 sockets have the IPV6_V6ONLY option enabled by
default. To allow the scripts to select the address family
via the --ip_version option transparently, disable the
IPV6_V6ONLY option implicilty on all sockets.
This fixes #132.

Sponsored by:	Netflix, Inc.

See https://github.com/google/packetdrill/commit/47582211690ffc2a7f40c371c19d283b2df26a44#diff-9b9398b17ceeb5025735f4c20d63a3e5L547

used by it.

Sponsored by:	Netflix

Don't check optval in getsockopt() when it call failed.
The value makes no sense.
While there, fix a memomry leak.

This patch is based on work by
Thadeu Lima de Souza Cascardo <cascardo@redhat.com>
It was manually merged, since the patch didn't apply cleanly.
The syscal was also added to the syntax highlighting files for
vim, emacs and bbedit.

When a blocking system call is ongoing, the error message shown was
wrong. It was indicated that a blocking system call is on-going when
the program terminates. This is correct, but hides the error message
which describes why packetdrill is terminating.

Sponsored by:	Netflix

Sponsored by:	Netflix

The thread name is only used for debugging. On Linux this
breaks is_thread_sleeping(), since it assumes that the
process or threadname contains no space. Just don't set
this on Linux, so avoid any problems.

Sponsored by Netflix

Sponsored by Netflix

This is required to support blocking system calls on FreeBSD.
Sponsored by Netflix.

This helps in debugging.