ahaggar-ast: fix output where component_ref is involved

Signed-off-by: Djalal Harouni <tixxdz@opendz.org>
walk-nodes: remove unnecessary output calls

Signed-off-by: Djalal Harouni <tixxdz@opendz.org>
print-nodes: add output_label_declaration() to print label_decl nodes

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