I finished my single copy pipe/fifo implementation.

Main changes:
* it's more a rewrite of pipe_read() and pipe_write().
Both functions were a nightmare of nested loops and gotos.
I wrote a test app - with the right timing multiple writers on a fifo
can race and then they busy loop in the current pipe_write() - adding
another set of goto's for single copy is imho a bad idea.

* slightly faster for non-zero copy transfers due to the code
simplification.

* No single copy for exactly 4096 byte writes, only > PIPE_BUF.
Single copy (and thus blocking) such writes could trigger bugs in user
space apps that errorneously assume that a pipe write of PIPE_BUF bytes
after a successful poll(POLLOUT) doesn't block even if O_NONBLOCK is not
set. It's not defined in posix or susv2, but no unix version I tested
blocks in such writes.

* on P II/350 single cpu it's a big win (~+70 % bw_pipe)

* if you run 2 instances on a dual cpu P II/350 it's a big win, but if
you run only one instance, then the bw_pipe processes will jump from one
cpu to the other and it's only a small improvement (~+15%).

I've attached the patch, the test app is at
http://colorfullife.com/~manfred/kiopipe/fail.cpp

Please test it!

--
	Manfred