Support for 'netsplice' engine

This IO engine does network transfers, but uses splice() to move data
to/from a socket to a pipe and vmsplice() to move that data to/from
user space.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
diff --git a/HOWTO b/HOWTO
index 4d103c8..3af4913 100644
--- a/HOWTO
+++ b/HOWTO
@@ -343,6 +343,9 @@
 				or receive, if the latter only the port
 				argument is used.
 
+			netsplice Like net, but uses splice/vmsplice to
+				map data and send/receive.
+
 			cpu	Doesn't transfer any data, but burns CPU
 				cycles according to the cpuload= and
 				cpucycle= options. Setting cpuload=85