Change urllib to use HTTPConnection rather than old HTTP class.

Change urllib to use HTTPConnection rather than old HTTP class.

The HTTP class is a backwards compatibility layer for the Python 1.5
API.  (The only remaining use in the std library is xmlrpclib.)

The current change makes urllib issue HTTP/1.0 requests with
HTTPConnection, because is accesses HTTPResponse.fp directly instead
of using the read() method.  Using fp directly interacts poorly with
persistent connections.  There are probably better solutions than the
current one, but this is a start.