WiredTiger changes for MongoDB 3.1.7
WiredTiger changes for MongoDB 3.1.8
WiredTiger changes for MongoDB 3.0.6
Message: WT-2038 During sweeps, only hold the handle list lock when removing handles from the list.
Message: WT-2038 Count and report the total number of data handles
Message: WT-2038 Immediately discard temporary handles from session caches.
This should mean that checkpoint locks don't accumulate waiting for a sweep.
Message: Merge pull request #2120 from wiredtiger/WT-2038
WT-2038 Discard checkpoint lock handles asap
Message: WT-2038 Fix cases where a tree could be discarded while marked as the next tree for eviction to walk.
(cherry picked from commit 393344d5d4b436fe3519cb8ab541bab22663553d)