Minimize impact of redo log sync during checkpoint.
More exception documentation.
Add DequeIndex class, optimized for deque-like workloads.
Add code comment.
Fix NPE in utility method.
DequeIndex uses a Lock, enabling deadlock detection.
Remove unused parameters from internal method.
Handle lock failure properly in DequeIndex.
Merge remote-tracking branch 'remotes/origin/master' into stream

Conflicts:
	src/main/java/org/cojen/tupl/TreeCursor.java