(https://github.com/bitcoin-core/leveldb/pull/15 should go in first, but filing it here for review/visibility/easy testing, do not merge)
When a leveldb corruption happens, report the filename of the file where corruptions happens. This will aid in diagnosing database corruption issues.
Adds a GetName() to all the environment file classes to make it possible to report a filename downstream.
Example:
02017-11-13 09:35:25 LevelDB read failure: Corruption: block checksum mismatch: /.../.bitcoin/regtest/blocks/index/000042.ldb
(travis is failing due to subtree merge, which is correct)