riostream: Add example program for using iomap routines.

riostream: Add example program for using iomap routines.

riostream is based on rstream, but uses the new riomap, riounmap,
and riowrite calls instead.  It runs a series of latency and
bandwidth tests using remote iomapped memory.

riostream is limited to using zero copy transfers at the
receiving side only at this time.

Signed-off-by: Sean Hefty <sean.hefty@intel.com>