Need to schedule compactions when manual compaction finishes

Summary: If there is an outstanding compaction scheduled but at the time a manual compaction is triggered, the manual compaction will preempt. In the end of the manual compaction, we should try to schedule compactions to make sure those preempted ones are not skipped.

Test Plan: make all check

Reviewers: yhchiang, ljin

Reviewed By: ljin

Subscribers: leveldb, dhruba, igor

Differential Revision: https://reviews.facebook.net/D21321
Include candidate files under options.db_log_dir in FindObsoleteFiles()

Summary: In FindObsoleteFiles(), we don't scan db_log_dir. Add it.

Test Plan: make all check

Reviewers: ljin, igor, yhchiang

Reviewed By: yhchiang

Subscribers: leveldb, yhchiang

Differential Revision: https://reviews.facebook.net/D21429
Changes to support unity build:
* Script for building the unity.cc file via Makefile
* Unity executable Makefile target for testing builds
* Source code changes to fix compilation of unity build
check prefix_size when using hash search in db_bench

Summary:
1. Check prefix_size when enable use_hash_search in db_bench
2. Remove include/statistics.h in db_bench

Test Plan: ./db_bench --use_hash_search=1

Reviewers: ljin, yhchiang, igor, sdong

Reviewed By: sdong

Subscribers: leveldb

Differential Revision: https://reviews.facebook.net/D21375
Merge pull request #228 from miguelportilla/develop

Changes to support unity build:

Script for building the unity.cc file via Makefile
Unity executable Makefile target for testing builds
Source code changes to fix compilation of unity build
make statistics ToString function empty instead of pure virtual

Summary: as title

Test Plan: make release

Reviewers: yhchiang, sdong

Reviewed By: sdong

Subscribers: leveldb

Differential Revision: https://reviews.facebook.net/D21549
Replace naked calls to operator new and delete (Fixes #222)

This replaces a mishmash of pointers in the Block and BlockContents classes with
std::unique_ptr. It also changes the semantics of BlockContents to be limited to
use as a constructor parameter for Block objects, as it owns any block buffers
handed to it.