Add a lot of missing Py_INCREF
diff --git a/OpenSSL/crypto/x509ext.c b/OpenSSL/crypto/x509ext.c
index 87fbcc3..3a7a101 100644
--- a/OpenSSL/crypto/x509ext.c
+++ b/OpenSSL/crypto/x509ext.c
@@ -303,6 +303,9 @@
         return 0;
     }
 
+    /* PyModule_AddObject steals a reference.
+     */
+    Py_INCREF((PyObject *)&crypto_X509Extension_Type);
     if (PyModule_AddObject(module, "X509ExtensionType",
                            (PyObject *)&crypto_X509Extension_Type) != 0) {
         return 0;