Better unaligned loads on arm
Better unaligned loads on arm

Now reverts to cg_llvm's default behavior of doing two aligned
loads and using vext to pull out a chunk of it.


Former-commit-id: 23b1ef37e517fcaa06b1c54093466376ec050f5a
darkbuck/Halide,Trass3r/Halide,darkbuck/Halide,Trass3r/Halide,Trass3r/Halide,darkbuck/Halide,darkbuck/Halide,Trass3r/Halide,darkbuck/Halide,darkbuck/Halide,Trass3r/Halide,Trass3r/Halide,darkbuck/Halide,Trass3r/Halide