Ahaggar: add the TREE_LIST node walker

Signed-off-by: Djalal Harouni <tixxdz@opendz.org>
Ahaggar: add the function decl arg walker

Signed-off-by: Djalal Harouni <tixxdz@opendz.org>
Ahaggar: add the FUNCTION_TYPE walker

Signed-off-by: Djalal Harouni <tixxdz@opendz.org>
Ahaggar: add more walker to the ahaggar_ast library

* TREE_LIST and TREE_BINFO walkers

* FUNCTION_TYPE and METHODE_TYPE walkers

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