The tests will manipulate the system daemon today, which can cause undesired
service interruption when the tests are run.

This change allows the geom_gate tests to be run with an arbitrary ggated(8)
daemon / geom_gate(4) device pairing.

Other changes:
- Sort #includes
- Use a more common idiom for parsing options with getopt(3)

Differential Revision: https://reviews.freebsd.org/D4836
MFC after: 2 weeks
Reviewed by: bjk (manpages), pjd (maintainer timeout)
Sponsored by: EMC / Isilon Storage Division

Reduce overlinking

^/user/gjb/hacking since this is likely to be merged to head/ soon.

Sponsored by:	The FreeBSD Foundation

inclusion of (at least) arm builds with the release.

Sponsored by:	The FreeBSD Foundation

by /etc/rc.d/jail.

performance in Xen's HVM mode.

Change communication protocol to be much more resistant on network
problems and to allow for much better performance.

Better performance is achieved by creating two connections between
ggatec and ggated one for sending the data and one for receiving it.
Every connection is handled by separeted thread, so there is no more
synchronous data flow (send and wait for response), now one threads
sends all requests and another receives the data.

Use two threads in ggatec(8):
- sendtd, which takes I/O requests from the kernel and sends them to the
  ggated daemon on the other end;
- recvtd, which waits for ggated responses and forwards them to the kernel.

Use three threads in ggated(8):
- recvtd, which waits for I/O requests and puts them onto incoming queue;
- disktd, which takes requests from the incoming queue, does disk operations
  and puts finished requests onto outgoing queue;
- sendtd, which takes finished requests from the outgoing queue and sends
  responses back to ggatec.

Because there were major changes in communication protocol, there is no
backward compatibility, from now on, both client and server has to run
on 5.x or 6.x (or at least ggated should be from the same FreeBSD version
on which ggatec is running).

For Gbit networks some buffers need to be increased. I use those settings:
kern.ipc.maxsockbuf=16777216
net.inet.tcp.sendspace=8388608
net.inet.tcp.recvspace=8388608
and I use '-S 4194304 -R 4194304' options for both, ggatec and ggated.

Approved by:	re (scottl)

Provoked by:	ru

Pointed out by:	ache, make buildworld