regent: Update stencil code to mark incomplete partitions as aliased.
regent: Update stencil code to mark incomplete partitions as aliased.

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