Mail charset error support

- Try multiple charset when no charset is specified by "Content-Type" field :
begins with sys.defaultencoding utf8
then "iso-8859-1", config file encoding and finally encoding found in previous
fields "Subject" or "From".

darcs-hash:20060201110843-86b55-7fd556a8ffadd9a5fed2b3317b17bfcca9d1dc58.gz

tests/email_generator.py

@@ -32,6 +32,9 @@ def _create_multipart(encoded):
         part2 = MIMEText("Encoded multipart2 with 'iso-8859-15' charset (<28><><EFBFBD>)", \
                          _charset = "iso-8859-15")
         msg.attach(part2)
+        part3 = MIMEText("Encoded multipart3 with no charset (<28><><EFBFBD>)", \
+                         _charset = "")
+        msg.attach(part3)
     else:
         part1 = MIMEText("Not encoded multipart1")
         msg.attach(part1)