It is now possible for orte_proc_applied_binding to be NULL (e.g., if
you mpirun --bind-to none), so we need to ensure we don't pass it down
to opal_hwloc_base_cset2*str().
Also, take the opprotunity to de-duplicate some strings that are used
in multiple places.
Refs trac:4073
This commit was SVN r30204.
The following Trac tickets were found above:
Ticket 4073 --> https://svn.open-mpi.org/trac/ompi/ticket/4073
b0b17c62aa