Adding cython v0.20.2 in third-party.

third_party/cython/src/Cython/Utility/ExtensionTypes.c

Index: third_party/cython/src/Cython/Utility/ExtensionTypes.c
diff --git a/third_party/cython/src/Cython/Utility/ExtensionTypes.c b/third_party/cython/src/Cython/Utility/ExtensionTypes.c
new file mode 100644
index 0000000000000000000000000000000000000000..423ed9673259123a9d16b5c55708e02d03bd4ebb
--- /dev/null
+++ b/third_party/cython/src/Cython/Utility/ExtensionTypes.c
@@ -0,0 +1,53 @@
+
+/////////////// CallNextTpDealloc.proto ///////////////
+
+static void __Pyx_call_next_tp_dealloc(PyObject* obj, destructor current_tp_dealloc);
+
+/////////////// CallNextTpDealloc ///////////////
+
+static void __Pyx_call_next_tp_dealloc(PyObject* obj, destructor current_tp_dealloc) {
+    PyTypeObject* type = Py_TYPE(obj);
+    /* try to find the first parent type that has a different tp_dealloc() function */
+    while (type && type->tp_dealloc != current_tp_dealloc)
+        type = type->tp_base;
+    while (type && type->tp_dealloc == current_tp_dealloc)
+        type = type->tp_base;
+    if (type)
+        type->tp_dealloc(obj);
+}
+
+/////////////// CallNextTpTraverse.proto ///////////////
+
+static int __Pyx_call_next_tp_traverse(PyObject* obj, visitproc v, void *a, traverseproc current_tp_traverse);
+
+/////////////// CallNextTpTraverse ///////////////
+
+static int __Pyx_call_next_tp_traverse(PyObject* obj, visitproc v, void *a, traverseproc current_tp_traverse) {
+    PyTypeObject* type = Py_TYPE(obj);
+    /* try to find the first parent type that has a different tp_traverse() function */
+    while (type && type->tp_traverse != current_tp_traverse)
+        type = type->tp_base;
+    while (type && type->tp_traverse == current_tp_traverse)
+        type = type->tp_base;
+    if (type && type->tp_traverse)
+        return type->tp_traverse(obj, v, a);
+    // FIXME: really ignore?
+    return 0;
+}
+
+/////////////// CallNextTpClear.proto ///////////////
+
+static void __Pyx_call_next_tp_clear(PyObject* obj, inquiry current_tp_dealloc);
+
+/////////////// CallNextTpClear ///////////////
+
+static void __Pyx_call_next_tp_clear(PyObject* obj, inquiry current_tp_clear) {
+    PyTypeObject* type = Py_TYPE(obj);
+    /* try to find the first parent type that has a different tp_clear() function */
+    while (type && type->tp_clear != current_tp_clear)
+        type = type->tp_base;
+    while (type && type->tp_clear == current_tp_clear)
+        type = type->tp_base;
+    if (type && type->tp_clear)
+        type->tp_clear(obj);
+}