Common.h: define the VERSION enum
Connection: fully rewritten HTTP parser

This parser is much easier to read and debug than the previous. Moreover,
it should fix the problem the previous one had with request pipelining.
The class still contains parts the old parser while the new one is in
development.
Connection::SimpleProtocolHandler: POST data handling fix
StringUtils::CmpI fix premature compare loop exit
QueryParams::AppendFormMultipart: boundary match checking fix

If the mismatching character in the source data actually matches the first
character of the boundary string, the parser state should be set
accordingly.
Moreover, the first character of the boundary string is always '\r', so
there's no need to check against the actual string.
Connection: remove the old parser completely