Added HALIDE_OUTPUT_FORWARD_CONST and appropriate usage
Added HALIDE_OUTPUT_FORWARD_CONST and appropriate usage

kgnk/Halide,psuriana/Halide,psuriana/Halide,kgnk/Halide,psuriana/Halide,kgnk/Halide,kgnk/Halide,kgnk/Halide,kgnk/Halide,psuriana/Halide,kgnk/Halide,kgnk/Halide,psuriana/Halide,psuriana/Halide,psuriana/Halide