Improve the check for header guard

Summary:
cpplint.py only recognize `#ifdef HEADER_GUARD` as header guard.
This patch enables the check for `#pragma once`.

Test Plan: New arc lint exclude the false alarm for `#pragma once`.

Reviewers: dhruba, sdong, igor, haobo

CC: leveldb

Differential Revision: https://reviews.facebook.net/D16227
First Transaction Logs Should Not Skip Storage Options Given

Summary: Currently, the first transaction log file ignore bytes_per_sync and other storage-related options. It is not consistent. Fix it.

Test Plan: make all check. See the options set in GDB.

Reviewers: haobo, kailiu

Reviewed By: haobo

CC: igor, ljin, yhchiang, leveldb, dhruba

Differential Revision: https://reviews.facebook.net/D16215
Enhancements to the API
Disable putting filter block to block cache

Summary: This bug caused server crash issues because the filter block is too big and kept purging out of cache.

Test Plan: Wrote a new unit tests to make sure it works.

Reviewers: dhruba, haobo, igor, sdong

Reviewed By: haobo

CC: leveldb

Differential Revision: https://reviews.facebook.net/D16221
Add a test in prefix_test to verify correctness of results

Summary:
Add a test to verify HashLinkList and HashSkipList (mainly for the former one) returns the correct results when inserting the same bucket in the different orders.

Some other changes:
(1) add the test to test list
(2) fix compile error
(3) add header

Test Plan: ./prefix_test

Reviewers: haobo, kailiu

Reviewed By: haobo

CC: igor, yhchiang, i.am.jin.lei, dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D16143
Update to CONTRIBUTING.md
allow lambda function syntax in cpplint

Summary: as title

Test Plan: arc lint

Reviewers: kailiu

Reviewed By: kailiu

CC: leveldb

Differential Revision: https://reviews.facebook.net/D16251
added a delete method for custom filter policy and merge operator to make it possible to override the cleanup behaviour of the return value
added a test case for custom merge operator
Update the instruction to build shared library
Merge pull request #82 from tecbot/api-enhancements

Enhancements to the API
A simple benchmark to measure WAL append latency

Summary: A simple benchmark that simulates WAL append. It can be used to test different platform/file system's performance on WAL.

Test Plan: run it.

Reviewers: haobo, kailiu

Reviewed By: haobo

CC: igor, dhruba, i.am.jin.lei, yhchiang, leveldb, nkg-

Differential Revision: https://reviews.facebook.net/D16239
Fix C API
DeleteFile should schedule Flush or Compaction

Summary:
More info here: https://github.com/facebook/rocksdb/issues/89
If flush fails because of ENOSPC, we have a deadlock problem. This is a quick fix that will continue the normal operation when user deletes the file and frees up the space on the device.

We need to address the issue more broadly with bg_error_ cleanup.

Test Plan: make check

Reviewers: dhruba, haobo, ljin

Reviewed By: ljin

CC: leveldb

Differential Revision: https://reviews.facebook.net/D16275
Merge remote-tracking branch 'origin/master'

Conflicts:
	db/c.cc
	include/rocksdb/c.h