Assume gfortran when building NumPy.
Bump mpfr version to 3.1.2.
Use LAPACKANDBLAS_DIR when ATLAS_DIR is not defined int petsc-hpc platform.
Use version 4.0.2 instead of current when building SuiteSparse.
Fix problem when building Python on systems that doesn't allow hard links.
Minor fix for helping CGAL pick correct Boost installation.
Use PYTHON_EXECUTABLE if defined when building DOLFIN.
Add platform file for the Abel Computing Cluster, using the GCC compilers.