Merge: Add debug option to compiler

Addition of a `-g` option to the compiler, right now it just disables gdb-side optimisation, but it may become more capable in the long run.

Pull-Request: #1615
Reviewed-by: Alexis Laferrière <alexis.laf@xymus.net>
Reviewed-by: Jean Privat <jean@pryen.org>
Reviewed-by: Alexandre Terrasa <alexandre@moz-code.org>

diff --cc src/compiler/abstract_compiler.nit
Simple merge