fix compile warning
fix release build
Include version in options
Improve ttl_test

Summary:
Our valgrind tests are failing because ttl_test is kind of flakey. This diff should fix valgrind issue and make ttl_test less flakey and much faster.

Instead of relying on Env::Default() for getting current time, I expose `Env*` to all TTL functions that are interested in time. That way, I can insert a custom test Env which is then used to provide exactly the times we need. That way, we don't need to sleep anymore -- we control the time.

Test Plan: ttl_test in normal and valgrind run

Reviewers: dhruba, haobo, sdong, yhchiang

Reviewed By: haobo

CC: leveldb

Differential Revision: https://reviews.facebook.net/D18399
Add TARGETS to gitignore
ApplyToAllCacheEntries

Summary: Added a method that executes a callback on every cache entry.

Test Plan: added a unit test

Reviewers: haobo

Reviewed By: haobo

CC: leveldb, dhruba

Differential Revision: https://reviews.facebook.net/D18441
link with lz4

Summary: link our fbcode build with lz4

Test Plan: compiles

Reviewers: sdong, haobo, dhruba, yhchiang

Reviewed By: yhchiang

CC: leveldb

Differential Revision: https://reviews.facebook.net/D18447
Add share_files_with_cheksum option to BackupEngine

Summary: added a new option to BackupEngine: if share_files_with_checksum is set to true, sst files are stored in shared_checksum/ and are identified by the triple (file name, checksum, file size) instead of just the file name. This option is targeted at distributed databases that want to backup their primary replica.

Test Plan: unit tests and tested backup and restore on a distributed rocksdb

Reviewers: igor

Reviewed By: igor

Differential Revision: https://reviews.facebook.net/D18393