memory manangement
------------------
- allow threads to dynamically enter and exit rcu's token passing ring
- augment rcu with heartbeat manager to kill and recover from stalled threads
- make rcu try yielding when its buffer gets full
- alternate memory reclamation schemes: hazard pointers and/or reference counting
- seperate nbd_malloc/nbd_free into general purpose malloc/free replacement

quality
-------
- verify the key memory management in list, skiplist, and hashtable
- transaction tests
- port perf tests from lib-high-scale
- characterize the performance of hashtable vs. skiplist vs. list
- validate function arguments in interface functions
- document usage of the library
- document algorithms

optimization
------------
- investigate 16 byte CAS; ht can store GUIDs inline instead of pointers to actual keys 
- shortcut from write-set to entries/nodes
- use a shared scan for write-set validation, similar to ht copy logic
- experiment with the performance impact of not passing the hash between functions in ht
- experiment with embedding the nstring keys in the list/skiplist nodes

features
--------
- allow values of 0 to be inserted into maps (change DOES_NOT_EXIST to something other than 0)