MPICH comes through?

[sawyl]

Following on from our attempts to get parallel HDF5 to pass its regression suite I've found that if I replace Parallel Environment MPI with MPICH, all the weird data mismatch failures disappear and the library passes its tests. This seems to rule out the OS, compilers, and file system as sources of the problem, and to bring the focus back on to PE MPI and its IO routines...