Summary:
I have manually audited the entire RocksJava code base.

Sorry for the large pull-request, I have broken it down into many small atomic commits though.

My initial intention was to fix the warnings that appear when running RocksJava on Java 8 with `-Xcheck:jni`, for example when running `make jtest` you would see many errors similar to:

```
WARNING in native method: JNI call made without checking exceptions when required to from CallObjectMethod
WARNING in native method: JNI call made without checking exceptions when required to from CallVoidMethod
WARNING in native method: JNI call made without checking exceptions when required to from CallStaticVoidMethod
...
```

A few of those warnings still remain, however they seem to come directly from the JVM and are not directly related to RocksJava; I am in contact with the OpenJDK hostpot-dev mailing list about these - http://mail.openjdk.java.net/pipermail/hotspot-dev/2017-February/025981.html.

As a result of fixing these, I realised we were not r
Closes https://github.com/facebook/rocksdb/pull/1890

Differential Revision: D4591758

Pulled By: siying

fbshipit-source-id: 7f7fdf4