Add simplification rules to help make vectorized boundary conditions to aligned boundaries simplify to dense vector loads/stores.
Add simplification rules to help make vectorized boundary conditions to aligned boundaries simplify to dense vector loads/stores.


Former-commit-id: 5caa319e4e213b3282b0ba9260c3de836b7cabed
darkbuck/Halide,Trass3r/Halide,darkbuck/Halide,Trass3r/Halide,darkbuck/Halide,darkbuck/Halide,Trass3r/Halide,Trass3r/Halide,darkbuck/Halide,darkbuck/Halide,Trass3r/Halide,Trass3r/Halide,darkbuck/Halide,Trass3r/Halide