size_t2s
_malloc_message("CPUs: ", size_t2s(ncpus, s), "\n", "");
_malloc_message("Pointer size: ", size_t2s(sizeof(void *), s),
_malloc_message("Quantum size: ", size_t2s(quantum, s), "\n", "");
_malloc_message("Max small size: ", size_t2s(small_max, s), "\n",
_malloc_message("Chunk size: ", size_t2s(chunksize, s), "", "");
_malloc_message(" (2^", size_t2s((size_t)opt_chunk_2pow, s),
static char *size_t2s(size_t x, char *s);