urllib,urllib2 -> urllib.request,urllib.error
urlparse -> urllib.parse
RobotParser -> urllib.robotparser

Updated tutorial references and other module references (http.client.rst,
ftplib.rst,contextlib.rst)
Updated the examples in the urllib2-howto

Addresses Issue3142.

I had to fix a few markup issues in controlflow.rst and modules.rst.

There's a unicode issue on line 448 in introduction.rst that someone else needs to fix.

codec changes in trubk and branch).  Hopefully the Py3k glossary wasn't
different from the trunk one.