Fix compile error with GCC 4.8 which doesn't have atomic operations for shared_ptr<>
Fix compile error with GCC 4.8 which doesn't have atomic operations for shared_ptr<>

ruiting/opencog,inflector/opencog,inflector/opencog,misgeatgit/opencog,inflector/opencog,ruiting/opencog,ruiting/opencog,ruiting/opencog,yantrabuddhi/opencog,andre-senna/opencog,inflector/opencog,andre-senna/opencog,inflector/opencog,inflector/opencog,yantrabuddhi/opencog,misgeatgit/opencog,andre-senna/opencog,shujingke/opencog,yantrabuddhi/opencog,AmeBel/opencog,shujingke/opencog,andre-senna/opencog,shujingke/opencog,yantrabuddhi/opencog,andre-senna/opencog,ruiting/opencog,shujingke/opencog,ruiting/opencog,misgeatgit/opencog,misgeatgit/opencog,shujingke/opencog,misgeatgit/opencog,AmeBel/opencog,AmeBel/opencog,AmeBel/opencog,misgeatgit/opencog,AmeBel/opencog,yantrabuddhi/opencog,shujingke/opencog,AmeBel/opencog,inflector/opencog,andre-senna/opencog,AmeBel/opencog,andre-senna/opencog,ruiting/opencog,shujingke/opencog,yantrabuddhi/opencog,inflector/opencog,misgeatgit/opencog,misgeatgit/opencog,misgeatgit/opencog,yantrabuddhi/opencog