ftplib module is currently lacking a test suite which actually connects
to a FTP server and uses the FTP class methods and facilities.
Bug #3911, discovered just a bunch of weeks before the stable release of
Python 3.0, is an example of how much a test suite is necessary.
As demanded by Benjamin Peterson in #3911, I started working on test
suite which implements an asyncore-based dummy FTP server which sends
fixed response codes that I used to test all the relevant FTP class methods.
Tests for the IPv6 module facilities are also included.
Although not that useful (IMHO) I didn't remove the old tests about
timeouts.

Tested against Python 2.6-RC2 on Windows XP SP3, Linux 2.6.20 and
FreeBSD 7.0.