Michael, Alex, here are the changes to return error codes from the mutex functions instead of aborting in place (this is the first part of the changes for WT-215).

Alex, would you please do the review and pull the changes when you're happy with them?

The interesting changes are mostly in the LSM code (although there are a couple of changes in conn_btree.c that are potentially tricky, and in how the eviction server is triggered).

I also fixed a few minor LSM locking problems I spotted by inspection when I was looking at some error cases, I put them on separate commits to make them easier to review.

Michael, once this change is in the tree, I'll add some kind of system-wide panic implementation, that will close out WT-215.