RFC 7230 compliant request-line parser based on Tokenizer API

RFC 7230 compliant request-line parser based on Tokenizer API

Refactor the request-line parser using a Tokenizer.

RFC 7230 requirements provide field terminator/delimiter limitations and
character sets for token validation. Also provides definitions of
boundaries for relaxed/tollerant parsing without needing Squid-specific
RFC violations.

This implementation is slightly stricter regarding whitespace in URLs
than previous implementation. It obeys a SHOULD requirement in RFC 7230
regarding responding with 400 status to those broken request messages.