user_encoding fix

[Nir Soffer]

I branched John A. Meinel encoding branch, and started with a small fix 
for user_encoding, described in 
http://bazaar.canonical.com/DarwinCommandLineArgumentDecoding.

See revisions 1575..1577 from http://nirs.dyndns.org/bzr/encoding-nirs

There are 3 new tests, 2 are trivial tests that check the correct 
value, the third is a test that try to validate the value of 
user_encoding by using shell completion and trying to decode the 
completed names, which is relevant to all posix like platforms.

Please comment and try the tests on your platform. I use here Mac OS X 
10.3, and have also a W2K machine but try to avoid it.


Best Regards,

Nir Soffer