- allows reuse of an int64_t scotch library with label-size 32
  and/or label-size 64.

COMP: prefer scotch/metis/kahip libraries with label-size qualifiers

- as noted in #2200, mpirun may insert mpi libraries higher in the
  library loader which can cause masking of our ThirdParty libraries
  of the same name. With scotch (for example), the operating system
  may have an int32 version installed but we have an int64 version
  compiled under ThirdParty. Runing in serial is fine, but in parallel
  we resolve to the (incorrect) system version due to the adjustments
  in mpirun.

- adjust the ThirdParty make scripts to also create corresponding
  links (eg, 'ln -s libscotch.so libscotch-int64.so') and prefer
  linkage with these qualified libraries.

    Eg,  -L$(SCOTCH_LIB_DIR) -lscotch$(SCOTCH_LIBNAME_SUFFIX)

  this prevent accidental runtime linkage with the system versions.

STYLE: simplify scotch interface code by using local functions