RDMA IO engine

I have hacked an rdma ioengine based on OFED for fio which could test
both rdma memory semantic (rdma_write/rdma_read) and channel semantic
(send/recv). Would you like to merge this engine into fio?

notes
1) RDMA engine works in IB, iWarp and RoCE.
2) RDMA engine is disable by default. To enable it, execute the following
   before compile:

$ export EXTFLAGS="-DFIO_HAVE_RDMA"
$ export EXTLIBS="-libverbs -lrdmacm"

Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
diff --git a/HOWTO b/HOWTO
index 85704ef..5e9b390 100644
--- a/HOWTO
+++ b/HOWTO
@@ -568,6 +568,11 @@
 
 				for more info on GUASI.
 
+			rdma    The RDMA I/O engine  supports  both  RDMA
+				memory semantic(RDMA_WRITE/RDMA_READ) and
+				channel semantic(Send/Recv) in InfiniBand, RoCE
+				and iWarp environment.
+
 			external Prefix to specify loading an external
 				IO engine object file. Append the engine
 				filename, eg ioengine=external:/tmp/foo.o