decode_rfc2231(): We need to urllib.unquote() the value even if the
charset and language fields are not present, e.g. as in:

    title*0="This%20is%20encoded"
diff --git a/Lib/email/Utils.py b/Lib/email/Utils.py
index 2b8b94f..a409e16 100644
--- a/Lib/email/Utils.py
+++ b/Lib/email/Utils.py
@@ -280,7 +280,7 @@
     import urllib
     parts = s.split("'", 2)
     if len(parts) == 1:
-        return None, None, s
+        return None, None, urllib.unquote(s)
     charset, language, s = parts
     return charset, language, urllib.unquote(s)