opal does not always define MB. It is recommended that opal_atomic_[rw]mb is
called instead. We will need to address the cases where these functions are
no-ops on weak-memory ordered cpus.
cmr=v1.7.5:ticket=trac:4158
This commit was SVN r30534.
The following Trac tickets were found above:
Ticket 4158 --> https://svn.open-mpi.org/trac/ompi/ticket/4158