STYLE: minor rewording, drop grep/sed in favour of sed only

- allows us to follow the changes

- improves code re-usage for pre-receive hook

- NB: A csh version is not needed, since the values here are only
      sourced during the wmake process

- for future updates of scotch, need to edit these two files:

    OpenFOAM-<VERSION>/src/parallel/decompose/Allwmake
    ThirdParty-<VERSION>/Allwmake