Add a default constructor to halide_type_t.
Add a default constructor to halide_type_t.

psuriana/Halide,jiawen/Halide,ronen/Halide,jiawen/Halide,ronen/Halide,jiawen/Halide,ronen/Halide,kgnk/Halide,psuriana/Halide,ronen/Halide,jiawen/Halide,psuriana/Halide,kgnk/Halide,jiawen/Halide,psuriana/Halide,ronen/Halide,ronen/Halide,kgnk/Halide,kgnk/Halide,psuriana/Halide,ronen/Halide,jiawen/Halide,kgnk/Halide,kgnk/Halide,ronen/Halide,psuriana/Halide,psuriana/Halide,kgnk/Halide,jiawen/Halide,kgnk/Halide