First cut concretization works, with tests.

lib/spack/spack/cmd/spec.py

lib/spack/spack/cmd/test.py

lib/spack/spack/concretize.py

lib/spack/spack/package.py

lib/spack/spack/spec.py

lib/spack/spack/test/concretize.py

lib/spack/spack/test/mock_packages/__init__.py

lib/spack/spack/test/mock_packages/callpath.py

lib/spack/spack/test/mock_packages/dyninst.py

lib/spack/spack/test/mock_packages/libdwarf.py

lib/spack/spack/test/mock_packages/libelf.py

lib/spack/spack/test/mock_packages/mpich.py

lib/spack/spack/test/mock_packages/mpileaks.py

lib/spack/spack/test/mock_packages_test.py

lib/spack/spack/test/spec_dag.py

lib/spack/spack/tty.py

lib/spack/spack/util/lang.py

lib/spack/spack/version.py