The proxy now dies somewhat gracefully when given a malformed request.
The `Content-Length' header is now only matched by the parser if its
value is an integer.
A request with a null or missing HTTP version in the header now defaults
to HTTP/1.0
A request with a null or missing `Host' header returns:
`ERROR: CrossDomain Request. The request was not sent.'
regardless of whether the host is specified in the URL.