Small fixes for the MCA variable interface.

 - Make a copy of enumerator data for default enumerators. This will allow
   the caller to free their data once the enumerator has been created. This
   is a change from just referencing the values array.

 - Make mca_base_pvar_notify check if the pvar is valid before calling the
   notify callback. This fixes a segmentation fault when destroying handles
   after MPI_Finalize().

cmr=v1.7.4:ticket=#3861
Add a bash completion script for orterun/mpirun.

Features of v 1.0:

 - Completion of all switches.
 - Completion of mca variable names.
 - Completion of mca variable values for enumerated variables and component
   selection variables.
 - Completion of --bind-to and --map-by.