Make is_strided_ramp understand strided ramps with undef elements.
Make is_strided_ramp understand strided ramps with undef elements.


Former-commit-id: b67fd2c1ea54fee8c159afefa6aaf86b633e8c2f
Trass3r/Halide,darkbuck/Halide,Trass3r/Halide,Trass3r/Halide,Trass3r/Halide,darkbuck/Halide,darkbuck/Halide,darkbuck/Halide,Trass3r/Halide,darkbuck/Halide,darkbuck/Halide,darkbuck/Halide,Trass3r/Halide,Trass3r/Halide