Output error stream if response code != 200

[Karr, David]

When testing of posting to web services, if the service returns a SOAP
fault, it will set the response code to 500.  However, the information
in the SOAP fault is still useful.  When wget gets a 500 response code,
it doesn't try to output the "error stream" (as opposed to the "input
stream"), where this information would be provided.  It might be useful
to add a command-line option that specifies to emit the error stream on
error.