test for "loadability" of libraries

Want the ability to check if given libraries can be loaded. For example, the petscFoam lib might be available but unloadable because the libpetsc.so isn't in the LD_LIBRARY_PATH.

@sbna

Easy enough to write a utility for this. Eg,

if Test-libraryLoad petscFoam
then
    echo "Yes it is loadable"
else
    echo "Forget it"
fi

Just need a good name for it. @andy