Make smartlist_add_all more efficient.

void

smartlist_add_all(smartlist_t *sl, const smartlist_t *s2)

{

  SMARTLIST_FOREACH(s2, void *, element, smartlist_add(sl, element));

  int n2 = sl->num_used + s2->num_used;

  if (n2 > sl->capacity) {

    int higher = sl->capacity * 2;

    while (n2 > higher)

      higher *= 2;

    sl->capacity = higher;

    sl->list = tor_realloc(sl->list, sizeof(void*)*sl->capacity);

  }

  memcpy(sl->list + sl->num_used, s2->list, s2->num_used*sizeof(void*));

  sl->num_used += s2->num_used;

}

/** Remove all elements E from sl such that E==element.  Preserve