Add missing forward of sliced() method to Buffer.h
Add missing forward of sliced() method to Buffer.h


Former-commit-id: 88114dbe458988959f3ee2bcee894feb011b3f3b
darkbuck/Halide,Trass3r/Halide,Trass3r/Halide,Trass3r/Halide,Trass3r/Halide,Trass3r/Halide,Trass3r/Halide,Trass3r/Halide,darkbuck/Halide,darkbuck/Halide,darkbuck/Halide,darkbuck/Halide,darkbuck/Halide,darkbuck/Halide