Fix bug in vectorize
Fix bug in vectorize

hiding vars in the scope wasn't working at all, because things were
indexed by their widened name instead of their original name


Former-commit-id: 68e6fa68c5b64de8c8313c82b78fdbaf43be7893
darkbuck/Halide,darkbuck/Halide,Trass3r/Halide,darkbuck/Halide,Trass3r/Halide,Trass3r/Halide,darkbuck/Halide,Trass3r/Halide,Trass3r/Halide,Trass3r/Halide,darkbuck/Halide,Trass3r/Halide,darkbuck/Halide,darkbuck/Halide