Ahaggar: add support to get the current input file

Signed-off-by: Djalal Harouni <tixxdz@opendz.org>
Ahaggar: minor improvments to the search next arg algorithm

Signed-off-by: Djalal Harouni <tixxdz@opendz.org>
Ahaggar: Make Parser() a new-class style like

Signed-off-by: Djalal Harouni <tixxdz@opendz.org>
Ahaggar: make Input() a new class style like

Signed-off-by: Djalal Harouni <tixxdz@opendz.org>
Ahaggar: just call parent super methodes of the Parser() class

Signed-off-by: Djalal Harouni <tixxdz@opendz.org>