Add peer certificate validation to SoapClient.
Add peer certificate validation to SoapClient.

This commit introduces a new idpMetadata parameter to SoapClient::send,
which is used to check peer certificate. If this parameter is present,
but no certData is set, an Exception will be raised.

Thanks to Adam Lantos for providing this patch.

rchavik/simplesamlphp,rchavik/simplesamlphp,rchavik/simplesamlphp,rchavik/simplesamlphp