Simplify tracks bounds for constant-sized loop vars, is more aggressive
Simplify tracks bounds for constant-sized loop vars, is more aggressive

For local laplacian, results in ~10% slower compilation and ~10% faster code


Former-commit-id: 44a2d82770c8db929a49ab9c096ba78e78136871
darkbuck/Halide,Trass3r/Halide,darkbuck/Halide,darkbuck/Halide,darkbuck/Halide,Trass3r/Halide,Trass3r/Halide,Trass3r/Halide,darkbuck/Halide,darkbuck/Halide,Trass3r/Halide,Trass3r/Halide,darkbuck/Halide,Trass3r/Halide