Upgrade LevelDB from 1.12 to 1.14:

* Fix issues 77, 87, 182, 190, 200, and 201

* Fix bug described in https://groups.google.com/d/msg/leveldb/yL6h1mAOc20/vLU64RylIdMJ

* Fix a bug where options.max_open_files was not getting clamped properly.

* Fix link to bigtable paper in docs.

* New sstables will have the file extension .ldb. .sst files will continue to be recognized.
Fix LevelDB Windows port