ENH: install helpers to assist when installing into system mpi directories

- the problem noted in issue #1893 is caused by the rpm-mpi-hooks
  (fedora and redhat-8).

  For the additional mpi library qualifier (openmpi-x86_64) to be
  added to the requirements, the mpi-specific libraries (eg,
  libPstream.so) need to be installed in the mpi system directory
  (eg, /usr/lib64/openmpi).

  However, need to then create symlinks to ensure that the libraries
  are correctly found via our LD_LIBRARY_PATH and we don't get dummy
  libraries.