HTTP: new parser and main structures refactoring

This is the first patch of a big change that is coming, it does:

  - deprecate mk_request.[ch]
  - deprecate mk_method.[ch]
  - replace struct client_session by struct mk_http_session
  - replace struct session_request by struct mk_http_request
  - new HTTP parser mk_http_parser.c

At this moment the server 'compiles'. It now needs to be aware about
the new parser and also needs some cleanup on headers interfaces.

the fun begins..

Signed-off-by: Eduardo Silva <eduardo@monkey.io>
HTTP: do not include old mk_method header file

Signed-off-by: Eduardo Silva <eduardo@monkey.io>
Core: small fixes when building in TRACE mode

Signed-off-by: Eduardo Silva <eduardo@monkey.io>
Core: refactoring structures and HTTP parser

Signed-off-by: Eduardo Silva <eduardo@monkey.io>
HTTP: merge parser results on http_request

Signed-off-by: Eduardo Silva <eduardo@monkey.io>
HTTP: more code cleanup (wip)

Signed-off-by: Eduardo Silva <eduardo@monkey.io>
Connection: link fixed http_request from http_session

Signed-off-by: Eduardo Silva <eduardo@monkey.io>
HTTP: little improvement when initializing parser.

Signed-off-by: Eduardo Silva <eduardo@monkey.io>
HTTP: re-enable support for Keep-Alive check.

This patch re-introduce the detection of the Connection header value
and do some logic steps to determinate if the connection should be
keep open as in a keep-alive state or be closed.

Signed-off-by: Eduardo Silva <eduardo@monkey.io>
Server: improve behavior when accepting a new connection

Signed-off-by: Eduardo Silva <eduardo@monkey.io>
Connection: fix body length passed to HTTP parser

Signed-off-by: Eduardo Silva <eduardo@monkey.io>
HTTP: Parser: fix handling of KA connections

Signed-off-by: Eduardo Silva <eduardo@monkey.io>
HTTP: Parser: fix iterator limit

Signed-off-by: Eduardo Silva <eduardo@monkey.io>
HTTP: Parser: validate Content-Length is set on POST/PUT requests

Signed-off-by: Eduardo Silva <eduardo@monkey.io>
HTTP: Parser: handle MK_CLIENT_REQUEST_ENTITY_TOO_LARGE

Signed-off-by: Eduardo Silva <eduardo@monkey.io>
HTTP: Core: initialize request and headers flags

Signed-off-by: Eduardo Silva <eduardo@monkey.io>
HTTP: Parser: validate protocol version

Signed-off-by: Eduardo Silva <eduardo@monkey.io>
HTTP: Parser: return BAD_REQUEST error on bad-formed protocol

Signed-off-by: Eduardo Silva <eduardo@monkey.io>
HTTP: Parser: extra checks on protocol and error page fixes

Signed-off-by: Eduardo Silva <eduardo@monkey.io>
HTTP: fix code indentation

Signed-off-by: Eduardo Silva <eduardo@monkey.io>