added free lists randomization step to malloc_bench
added free lists randomization step to malloc_bench

xiaoyur347/gperftools,acmorrow/gperftools,gperftools/gperftools,alk/gperftools,romange/gperftools,acmorrow/gperftools,gperftools/gperftools,rzinsly/gperftools,alk/gperftools,romange/gperftools,rzinsly/gperftools,acmorrow/gperftools,alk/gperftools,xiaoyur347/gperftools,xiaoyur347/gperftools,romange/gperftools,rzinsly/gperftools,gperftools/gperftools,rzinsly/gperftools,alk/gperftools,gperftools/gperftools,xiaoyur347/gperftools,romange/gperftools,acmorrow/gperftools