Improves compliance with RFC 7230 on the expected handling of requests
that have URI or asterisk in the request target.
This means rejecting asterisk requests that are not OPTIONS and rejecting
authority-form requests taht are not CONNECT.
This also means the server will handle the path and query on targets
with absolute URIs as request-targets.
* Use ascii decoding routine that disallows null chars
- GetAsciiString() in newer corefxlab builds allows 0 (which is a valid
ascii char). To avoid future regressions, GetAsciiStringNonNullCharacters()
was added and used in place of GetAsciiString() when interpreting the
request line and headers
- Make GetAsciiStringNonNullCharacters return empty instead of null