Testing needed for new pipe code (in master)

    I have substantially rewritten kern/sys_pipe.c, which is our support
    for pipes.  It should work quite well on a SMP box now.  Performance
    on UP boxes might be a bit lower then the old code but the difference
    should not be noticable for any production workload.

    To test the SMP improvements set sysctl kern.pipe.mpsafe=1.

    The latest code significantly improves synchronous communication over
    a pipe (not a socket, sorry), reducing (Awrite,Bread,Bwrite,Aread)
    sequences from 7uS to 2uS on my test box.  The pipe1 test (from
    /usr/src/test/sysperf) tests this.

    The latest code is now able to fully saturated all available cpus
    when running multiple copies of the pipe2 test (from
    /usr/src/test/sysperf).

						-Matt