backport jhylton's checkin of

backport jhylton's checkin of
    revision 1.45 of httplib.py

SF bug report #405939: wrong Host header with proxy

In August, Greg said this looked good, so I'm going ahead with it.

The fix is different from the one in the bug report.  Instead of using
a regular expression to extract the host from the url, I use
urlparse.urlsplit.

Martin commented that the patch doesn't address URLs that have basic
authentication username and password in the header.  I don't see any
code anywhere in httplib that supports this feature, so I'm not going
to address it for this fix.

Bug fix candidate.