fix compile error under Mac OS X
fix_sst_dump_for_old_sst_format

Summary:
1. fix segment error when dumping old sst format (no properties nor stats)
2. Enable dumpping old sst format

Test Plan:
Generate block based sst file with "properties", and one with "stats" and one without neither.
Read it using sst_dump

Reviewers: ljin, igor, yhchiang, dhruba, sdong

Reviewed By: sdong

Subscribers: leveldb

Differential Revision: https://reviews.facebook.net/D21837
[Java] Add purgeOldBackups API

Summary:
1. Check status of CreateNewBackup. If status is not OK, then throw.
2. Add purgeOldBackups API

Test Plan:
make test
make sample

Reviewers: haobo, sdong, zzbennett, swapnilghike, yhchiang

Reviewed By: yhchiang

Subscribers: leveldb

Differential Revision: https://reviews.facebook.net/D21753
Support purging logs from separate log directory

Summary:
1. Support purging info logs from a separate paths from DB path. Refactor the codes of generating info log prefixes so that it can be called when generating new files and scanning log directory.
2. Fix the bug of not scanning multiple DB paths (should only impact multiple DB paths)

Test Plan:
Add unit test for generating and parsing info log files
Add end-to-end test in db_test

Reviewers: yhchiang, ljin

Reviewed By: ljin

Subscribers: leveldb, igor, dhruba

Differential Revision: https://reviews.facebook.net/D21801
Fix autovector iterator increment/decrement comments

Summary: The prefix and postfix operators were mixed up in the autovector class.

Test Plan: Inspection

Reviewers: sdong, kailiu

Reviewed By: kailiu

Differential Revision: https://reviews.facebook.net/D21873
Fix typo huage => huge

Test Plan: Inspection

Reviewers: sdong

Reviewed By: sdong

Differential Revision: https://reviews.facebook.net/D21891
Merge pull request #234 from bbiao/master

fix compile error under Mac OS X