Cross platform fix for Java benchmark shell script.

java/jdb_bench.sh

@@ -1 +1,7 @@
-java -server -d64 -XX:NewSize=4m -XX:+AggressiveOpts -Djava.library.path=.:../ -cp "rocksdbjni.jar:.:./*" org.rocksdb.benchmark.DbBenchmark $@
+PLATFORM=64
+if [ `getconf LONG_BIT` != "64" ]
+then
+  PLATFORM=32
+fi
+echo "Running benchmark in $PLATFORM-Bit mode."
+java -server -d$PLATFORM -XX:NewSize=4m -XX:+AggressiveOpts -Djava.library.path=.:../ -cp "rocksdbjni.jar:.:./*" org.rocksdb.benchmark.DbBenchmark $@