Add missing std namespace
Add missing std namespace

AmeBel/opencog,andre-senna/opencog,andre-senna/opencog,andre-senna/opencog,andre-senna/opencog,andre-senna/opencog,AmeBel/opencog,AmeBel/opencog,andre-senna/opencog,AmeBel/opencog,AmeBel/opencog,andre-senna/opencog,AmeBel/opencog,AmeBel/opencog