Resolution of bug #997368, "strftime() backward compatibility".

Specifically, time.strftime() no longer accepts a 0 in the yday position of a
time tuple, since that can crash some platform strftime() implementations.

parsedate_tz(): Change the return value to return 1 in the yday position.

Update tests in test_rfc822.py and test_email.py

Lib/test/test_rfc822.py

@@ -53,7 +53,7 @@ class MessageTestCase(unittest.TestCase):
         out = m.getdate('date')
         if out:
             self.assertEqual(out,
-                             (1999, 1, 13, 23, 57, 35, 0, 0, 0),
+                             (1999, 1, 13, 23, 57, 35, 0, 1, 0),
                              "date conversion failed")