gnulib-tool.py: Make use of GLModule's __hash__ method. * pygnulib/GLModuleSystem.py (GLModuleTable.addUnconditional) (GLModuleTable.isConditional): Use the GLModule object instead of the module name directly. (GLModuleTable.addConditional, GLModuleTable.getCondition): Likewise. Use a tuple of two GLModule objects as a key for the conditionals dictionary.