MPI-2:6.3.4 says about reduction operations
* Have the point-to-point one-sided component spew a warning and return
an error if a non-predefined datatype is used with an MPI_OP other
than MPI_REPLACE. Yes, this violates the MPI standard, but it's the
best we can do until George and I implement support for figuring out
where all the locations to update are..
This commit was SVN r9134.