Add #ifdef PY_USING_UNICODE sections, so that
stringobject.c compiles again with --disable-unicode.

Fixes SF bug http://www.python.org/sf/554912
diff --git a/Objects/stringobject.c b/Objects/stringobject.c
index 5bad04e..6c18add 100644
--- a/Objects/stringobject.c
+++ b/Objects/stringobject.c
@@ -1457,6 +1457,7 @@
 	if (sep != NULL && sep != Py_None) {
 		if (PyString_Check(sep))
 			return do_xstrip(self, striptype, sep);
+#ifdef Py_USING_UNICODE
 		else if (PyUnicode_Check(sep)) {
 			PyObject *uniself = PyUnicode_FromObject((PyObject *)self);
 			PyObject *res;
@@ -1467,9 +1468,14 @@
 			Py_DECREF(uniself);
 			return res;
 		}
+#endif
 		else {
 			PyErr_Format(PyExc_TypeError,
+#ifdef Py_USING_UNICODE
 				     "%s arg must be None, str or unicode",
+#else
+				     "%s arg must be None or str",
+#endif
 				     STRIPNAME(striptype));
 			return NULL;
 		}