mk_queue: Add pipe support.
mk_scheduler: Add sockaddr member to sched_connection.

Add sockaddr and sock_len arguments to mk_sched_register(),
mk_sched_connection_claim().
mk_plugin_next: Add mk_response_add_headers().

Add a block of headers to response.
mk_http: Make mk_http_request_header() public.

Fetches headers from mk_request_info.
mk_plugin_next: Trace header printing fixup.
mk_log: Add log module.
mk_http: Log requests.
Cleanup session_request and rename it mk_request.

This removes all members used by the old plugin system.
Cleanup client_session, move and rename mk_http_session.
mk_scheduler: Add support for connections without timeout.
mk_log: Add configuration and write to file support.
mk_http_transport: Ignore 0 byte chunks.
mk_http_transport: Use mk_http_transport as argument.
mk_http_transport: Remove mk_request.h/mk_header.h dependency.
Use mk_request in plugins.
mk_user: Remove mk_user.
mk_method: Remove mk_method.
mk_filter: If there are no filters, assume nothing is filtered.
mk_log: Print 'plain/text' if no type set for response.
mk_mimetype: Don't add '\r\n' after mime type.