parser-ng: Add HTTP/1.x extension tokenizer

Adds a class Http1::Tokenizer, which inherits from ::Parser::Tokenizer
and presents additional HTTP-specific token parsing methods.

At present it extends for the quoted-string, 1#( token/ quoted-string ),
and qdtext constructs from RFC 7230 and RFC 1945.

It can also cope with charset and quoted-pair escaping differences in
qdtext between RFC 1945 and RFC 7230. The un-escaped form of token is
returned.