[openib-general] RMPP implementation

[Sean Hefty]

I'm starting work on the RMPP implementation in the MAD code.  If anyone 
has any ideas/preferences on the implementation, please let me know.

For the send side, there are a couple of ways to perform the segmentation:

1.  Issue one send at a time.  Additional sends are not transfered until 
  the first send completes.
2.  Issue multiple sends using 2 data segments per request.  This 
requires allocating and mapping space (36 bytes) for copying the MAD 
common and RMPP headers.
3.  Issue multiple sends using 3 data segments per request.  This is the 
same as #2, but only copes the RMPP header.

I'm leaning towards #2 at this point.

RMPP is fairly complex, so I will probably submit a series of patches, 
rather than the entire implementation at once.

- Sean