Resolve patch #449367.

For the HTTPS class (when available), ensure that the x509 certificate data
gets passed through to the HTTPSConnection class. Create a new
HTTPS.__init__ to do this, and refactor the HTTP.__init__ into a new _setup
method for both init's to call.

Note: this is solved differently from the patch, which advocated a new
**x509 parameter on the base HTTPConnection class. But that would open
HTTPConnection to arbitrary (ignored) parameters, so was not as desirable.