minor changes to the python api.

- pep8 script was giving an error on non utf8 scons source files.
- use PyList_SET_ITEM macro when list type is ensured.
- all mathutils types use subtypes to create new types when available.
- use defines MAT3_UNITY, MAT4_UNITY to initialize unit matrices.

source/blender/python/generic/mathutils_geometry.c

@@ -435,7 +435,7 @@ static PyObject *M_Geometry_PolyFill(PyObject *UNUSED(self), PyObject * polyLine
 		index= 0;
 		dl_face= dl->index;
 		while(index < dl->parts) {
-			PyList_SetItem(tri_list, index, Py_BuildValue("iii", dl_face[0], dl_face[1], dl_face[2]) );
+			PyList_SET_ITEM(tri_list, index, Py_BuildValue("iii", dl_face[0], dl_face[1], dl_face[2]) );
 			dl_face+= 3;
 			index++;
 		}