[Mpi3-hybridpm] External interfaces chapter updates

[Pavan Balaji]

Folks,

I think it's time for us to start dumping in text into the chapter and 
start discussing the exact wording. I've included the helper threads and 
shared memory extensions proposals into the chapter and uploaded it to 
the wiki 
(https://svn.mpi-forum.org/trac/mpi-forum-web/attachment/wiki/MPI3Hybrid/ei-2-v0.1.pdf). 
Please take a look at it and let me know your comments.

Marc is still making some changes to the endpoints proposal. I'll add it 
in once the changes are done.

  -- Pavan

-- 
Pavan Balaji
http://www.mcs.anl.gov/~balaji