Ahaggar: add helper to extract function decl name

Signed-off-by: Djalal Harouni <tixxdz@opendz.org>
Ahaggar: major improvements on gcc module

* Add the OP_SYMBOL table
* Remove the useless 'self' argument since we do not use OO style

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