halide_memoization_cache_cleanup() needs to null the MRU and LRU globals
halide_memoization_cache_cleanup() needs to null the MRU and LRU globals

Otherwise they can point to dangling memory and fun ensues


Former-commit-id: c4f3dc82e827f73502277ec53bf369a93b085bb7
Trass3r/Halide,darkbuck/Halide,Trass3r/Halide,Trass3r/Halide,Trass3r/Halide,darkbuck/Halide,darkbuck/Halide,Trass3r/Halide,Trass3r/Halide,darkbuck/Halide,darkbuck/Halide,darkbuck/Halide,Trass3r/Halide,darkbuck/Halide