Added clear cache methods to clear the internal type lookup cache for ref leak test runs.

Python/sysmodule.c

@@ -754,6 +754,17 @@ a 11-tuple where the entries in the tuple are counts of:\n\
 10. Number of stack pops performed by call_function()"
 );
 
+static PyObject *
+sys_cleartypecache(PyObject* self, PyObject* args)
+{
+	PyType_ClearCache();
+	Py_RETURN_NONE;
+}
+
+PyDoc_STRVAR(cleartypecache_doc,
+"_cleartypecache() -> None\n\
+Clear the internal type lookup cache.");
+
 #ifdef __cplusplus
 extern "C" {
 #endif
@@ -776,6 +787,8 @@ static PyMethodDef sys_methods[] = {
 	/* Might as well keep this in alphabetic order */
 	{"callstats", (PyCFunction)PyEval_GetCallStats, METH_NOARGS,
 	 callstats_doc},
+	{"_cleartypecache", sys_cleartypecache, METH_NOARGS,
+	 cleartypecache_doc},
 	{"_current_frames", sys_current_frames, METH_NOARGS,
 	 current_frames_doc},
 	{"displayhook",	sys_displayhook, METH_O, displayhook_doc},