Per 0ab6b201fe, note in the MPI_Comm_spawn_multiple.3in man page that
the array_of_commands does not need to be terminated -- it just need
to have exactly "count" entries. In the Fortran binding, at least,
this is different than in prior released versions of Open MPI (it's
not a backwards incompatibility, since prior versions of Open MPI
required array_of_commands to be blank-string-terminated in Fortran --
this change makes Open MPI be *less* restrictive, and therefore still
backwards compatible).
Signed-off-by: Jeff Squyres <jsquyres@cisco.com>