Ahaggar: add the ahaggar_ast_format sample

Signed-off-by: Djalal Harouni <tixxdz@opendz.org>
Ahaggar: note that this is currently only a sample

Signed-off-by: Djalal Harouni <tixxdz@opendz.org>
Ahaggar: iterate over operands

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