[MERGE] provide lock debugging in tests

[Martin Pool]

Martin Pool has voted resubmit.
Status is now: Resubmit
Comment:
It's much better to have options that turn on debug trace not cause side 
effects; please use -Dlock_checks or something instead.

It seems like it would not be much harder to check that they are 
actually paired up and print the one

For details, see: 
http://bundlebuggy.aaronbentley.com/request/%3C1207281795.5960.161.camel%40lifeless-64%3E