Added preallocated buffer to speed up halide_malloc/free
Added preallocated buffer to speed up halide_malloc/free


Former-commit-id: be14364e9e45b42f5fddd0a29061f873651ea4e5
darkbuck/Halide,Trass3r/Halide,darkbuck/Halide,darkbuck/Halide,Trass3r/Halide,darkbuck/Halide,Trass3r/Halide,Trass3r/Halide,Trass3r/Halide,darkbuck/Halide,Trass3r/Halide,darkbuck/Halide,Trass3r/Halide,darkbuck/Halide