Make Java Client compilable.

Summary:
Debug and ported changes from the Open Source Github repo to our repo.
Wrote a script to easy build the java Library. future compiling java lib should just be running this script.

Test Plan: it compiles.

Reviewers: dhruba, leveldb

Reviewed By: dhruba

Differential Revision: https://reviews.facebook.net/D7323

build_java.sh

@@ -0,0 +1,14 @@
+#!/bin/bash -e
+cd $LEVELDB_HOME
+git apply $LEVELDB_HOME/java/leveldbjni/db.h.patch
+make clean libleveldb.a
+cd $LEVELDB_HOME
+cd java/leveldb/leveldb-api
+mvn clean package
+export JAVA_HOME=/usr/local/jdk-6u14-64/
+export LEVELDBJNI_HOME=$LEVELDB_HOME/java/leveldbjni/
+export SNAPPY_HOME=/home/dhruba/snappy-1.0.5
+cd $LEVELDBJNI_HOME
+mvn clean install -P linux64
+cd $LEVELDB_HOME
+git checkout $LEVELDB_HOME/include/leveldb/db.h