[JNI] Add java api and java tests for WriteBatch and WriteOptions, add put() and remove() to RocksDB.

Summary:
* Add java api for rocksdb::WriteBatch and rocksdb::WriteOptions, which are necessary components
  for running benchmark.
* Add java test for org.rocksdb.WriteBatch and org.rocksdb.WriteOptions.
* Add remove() to org.rocksdb.RocksDB, and add put() and remove() to RocksDB which take
  org.rocksdb.WriteOptions.

Test Plan: make jtest

Reviewers: haobo, sdong, dhruba

Reviewed By: sdong

CC: leveldb

Differential Revision: https://reviews.facebook.net/D17373
[JNI] Improve the internal interface between java and c++ for basic db operations.

Summary:
Improve the internal interface between java and c++ for basic db operations
by including the RocksDB native handle (i.e., c++ pointer of rocksdb::DB)
as a input parameter of the internal interface.

This improvement reduces one JNI call per db operation from c++.

Test Plan: make test

Reviewers: haobo, sdong, dhruba

Reviewed By: sdong

CC: leveldb

Differential Revision: https://reviews.facebook.net/D17445
[JNI] Avoid a potential byte-array-copy btw c++ and java in RocksDB.get(byte[], byte[]).

Summary: Avoid a JNI call to GetByteArrayElements, which may introduce a byte-array-copy.

Test Plan: make jtest

Reviewers: haobo, sdong, dhruba

CC: leveldb

Differential Revision: https://reviews.facebook.net/D17451
Merge branch 'master' into jni
Flush Buffered Info Logs Before Doing Compaction (one line change)

Summary: Flushing log buffer earlier to avoid confusion of time holding the locks.

Test Plan: Should be safe as long as several related db test passes

Reviewers: haobo, igor, ljin

Reviewed By: igor

CC: nkg-, leveldb

Differential Revision: https://reviews.facebook.net/D17493
Merge branch 'jni'
Make RocksDB compile for iOS

Summary:
I had to make number of changes to the code and Makefile:
* Add `make lib`, that will create static library without debug info. We need this to avoid growing binary too much. Currently it's 14MB.
* Remove cpuinfo() function and use __SSE4_2__ macro. We actually used the macro as part of Fast_CRC32() function.
As a result, I also accidentally fixed this issue: https://www.facebook.com/groups/rocksdb.dev/permalink/549700778461774/?stream_ref=2
* Remove __thread locals in OS_MACOSX

Test Plan: `make lib PLATFORM=IOS`

Reviewers: ljin, haobo, dhruba, sdong

Reviewed By: haobo

CC: leveldb

Differential Revision: https://reviews.facebook.net/D17475
Dynamically choose SSE 4.2

Summary: Otherwise, if we compile on machine with SSE4.2 support and run it on machine without the support, we will fail.

Test Plan: compiles, verified that isSse42() gets called.

Reviewers: dhruba

Reviewed By: dhruba

CC: leveldb

Differential Revision: https://reviews.facebook.net/D17505
make hash_link_list Node's key space consecutively followed at the end

Summary: per sdong's request, this will help processor prefetch on n->key case.

Test Plan: make all check

Reviewers: sdong, haobo, igor

Reviewed By: sdong

CC: leveldb

Differential Revision: https://reviews.facebook.net/D17415
Create log::Writer out of DB Mutex

Summary: Our measurement shows that sometimes new log::Write's constructor can take hundreds of milliseconds. It's unclear why but just simply move it out of DB mutex.

Test Plan: make all check

Reviewers: haobo, ljin, igor

Reviewed By: haobo

CC: nkg-, yhchiang, leveldb

Differential Revision: https://reviews.facebook.net/D17487
Remove -Wno-unused-const-variable
relax backupable db rate limit tests
Update HISTORY.md

Summary: Update HISTORY.md to make existing items to 2.8 release and add something I think is missing.

Test Plan: N/A

Reviewers: haobo, igor, ljin, dhruba, yhchiang, xjin

Reviewed By: haobo

CC: leveldb

Differential Revision: https://reviews.facebook.net/D17517