More email package related repairs.  This fixes smtplib's import and use of
email.base64mime, but test_smtplib still has failures for me.  They are
timeout errors so think they're more related to my current wacky network setup
than bugs remaining in the code related to the email package.

This also r57693 that got clobbered with the sandbox sync, and fixes a couple
of other minor problems that cropped up.  I will kill the sandbox branch next.

The email package now has 11F/11E.
diff --git a/Lib/email/test/test_email.py b/Lib/email/test/test_email.py
index 78d702d..f7cac97 100644
--- a/Lib/email/test/test_email.py
+++ b/Lib/email/test/test_email.py
@@ -2538,10 +2538,8 @@
 
     def test_decode(self):
         eq = self.assertEqual
-        eq(base64mime.decode(''), '')
+        eq(base64mime.decode(''), b'')
         eq(base64mime.decode('aGVsbG8='), b'hello')
-        eq(base64mime.decode('aGVsbG8=', 'X'), b'hello')
-        eq(base64mime.decode('aGVsbG8NCndvcmxk\n', 'X'), b'helloXworld')
 
     def test_encode(self):
         eq = self.assertEqual