LU-9121 lnet: Add the userspace Marshalling API

LU-9121 lnet: Add the userspace Marshalling API

Given a UDSP and a memory block of size
enough to hold a marshalled udsp, marshal
the UDSP pointed to by udsp into the memory block.

Change-Id: I67e9c2cc0d7f3dab1e968019d5ee546e6fefeba3
Test-Parameters: trivial testlist=lnet-selftest,sanity-lnet
Signed-off-by: Sonia Sharma <sharmaso@whamcloud.com>
Reviewed-on: https://review.whamcloud.com/34513
Reviewed-by: Sebastien Buisson <sbuisson@ddn.com>
Reviewed-by: Serguei Smirnov <ssmirnov@whamcloud.com>
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Amir Shehata <ashehata@whamcloud.com>