AutotoolsPackage: minor improvements (#2859)

* AutotoolsPackage: added configure_directory to permit build out of source. The configure script executable is now invoked with an absolute path. Modified a few packages accordingly.

* build_systems: functions returning directories are now properties

* build_systems: fixed issues with tcl and tk

* AutotoolsPackage: reworked recipe for autoreconf

var/spack/repos/builtin/packages/py-pypar/package.py

@@ -37,8 +37,7 @@ class PyPypar(PythonPackage):
     depends_on('mpi')
     depends_on('py-numpy', type=('build', 'run'))
 
+    build_directory = 'source'
+
     def url_for_version(self, version):
         return "https://storage.googleapis.com/google-code-archive-downloads/v2/code.google.com/pypar/pypar-%s.tgz" % version
-
-    def build_directory(self):
-        return 'source'