Test not passed. Need further debugging.

old/ -> misc/

Record a failed attempt to formally prove the MT-safety of LWMalloc.

* Statically initialize _rtree_lock in order to avoid potential malloc() call
  inside pthread_mutex_init().
* Update comments.

I've just added it into the LWMalloc build system, without using
LWMalloc at all. Further study & modification of this benchmark
is needed.