antithread/queue: fast fixed-length queue implementation.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
antithread/queue: speed multi-producers case by using odd numbers as a lock.

This brings us pretty close to the previous exclusive-producer and
exclusive-consumer cases.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
patch queue-discard-bench.patch
patch queue-bsd-style.patch
antithread/queue: remove exclusive accessors.

Since it seems to be a wash performance-wise, remove them.  Done as a
separate commit, in case I'm wrong.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
patch HAVE_FUTEX.patch
patch notify.patch
patch queue-use-notify.patch