nitcorn: force delete session cookie when no session associated to response

Signed-off-by: Alexis Laferrière <alexis.laf@xymus.net>
nitcorn: harden request processing

Signed-off-by: Alexis Laferrière <alexis.laf@xymus.net>
contrib: intro of tnitter

Signed-off-by: Alexis Laferrière <alexis.laf@xymus.net>
Merge: Tnitter

Look only at the last 3 commits, the first part is from #620.

Almost the same version as what is running at http://tnitter.xymus.net/.

Pull-Request: #631
Reviewed-by: Lucas Bajolet <r4pass@hotmail.com>
Reviewed-by: Jean Privat <jean@pryen.org>