net: fix warning for systems without TCP_NODELAY

Signed-off-by: Jens Axboe <axboe@kernel.dk>
Fix compile of RDMA engine for SunOS 5.x

- byteswap.h include that doesn't exist there. Kill it, we
  have no use for it.

- No RLIMIT_MEMLOCK on SunOS. The use in the engine is a bit
  suspect, so not a problem if we don't have it. Add configure
  check for that.

Signed-off-by: Jens Axboe <axboe@kernel.dk>