legion: fix for old gcc versions that do not support all of c++11
legion: fix for old gcc versions that do not support all of c++11

StanfordLegion/legion,StanfordLegion/legion,StanfordLegion/legion,StanfordLegion/legion,StanfordLegion/legion,StanfordLegion/legion,StanfordLegion/legion,StanfordLegion/legion