This commit removes the --with-mpi-thread-multiple option and forces
MPI_THREAD_MULTIPLE support. This cleans up an abstration violation
in opal where OMPI_ENABLE_THREAD_MULTIPLE determines whether the
opal_using_threads is meaningful. To reduce the performance hit on
MPI_THREAD_SINGLE programs an OPAL_UNLIKELY is used for the
check on opal_using_threads in OPAL_THREAD_* macros.
This commit does not clean up the arguments to the various functions
that take whether muti-threading support is enabled. That should be
done at a later time.
Signed-off-by: Nathan Hjelm <hjelmn@lanl.gov>