regent: Make the optimize_config_options scan the AST only once
regent: Make the optimize_config_options scan the AST only once

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