HTTP support improvements:
* RFC2616 compliance
* Case insensitive equality, inequality operators for strings
* Improvements to http::parser
* Tidy up HTTP method enumeration
HTTP handshake in peer protocol (RIPD-351):
* New I/O paths for client and server role
* New handshake_analyzer detects the peer protocol
* New basic_message class for parsing and storing HTTP messages
* Conditional compilation for selective feature enabling.
* Server supports both current handshake and HTTP handshake