regent: Add unsafe cast case in vectorizer
regent: Add unsafe cast case in vectorizer

sdalton1/legion,StanfordLegion/legion,sdalton1/legion,sdalton1/legion,StanfordLegion/legion,StanfordLegion/legion,chuckatkins/legion,StanfordLegion/legion,chuckatkins/legion,StanfordLegion/legion,chuckatkins/legion,chuckatkins/legion,sdalton1/legion,StanfordLegion/legion,StanfordLegion/legion,chuckatkins/legion,chuckatkins/legion,sdalton1/legion,chuckatkins/legion,sdalton1/legion,StanfordLegion/legion