[Mpi3-rma] MPI_NO_OP and origin buffer

[Jim Dinan]

Hi All,

It looks like we forgot to specify that for MPI_NO_OP in the new 
accumulate ops, the origin buffer is ignored (i.e. it's acceptable to 
pass NULL).  We can add this text on page 441, line 30:

When MPI_NO_OP is specified, the origin buffer is ignored.

We already have such a use case in the linked list example.

  ~Jim.