Ahaggar: add the gcc.py module

* This module contains various helpers

Signed-off-by: Djalal Harouni <tixxdz@opendz.org>
Ahaggar: import the gcc.py module

Signed-off-by: Djalal Harouni <tixxdz@opendz.org>
Ahaggar: make gcc_tree.TREE a dictionary

* Since scripts will reference code by strings then turn TREE into a
  dict referenced by string codes.

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