use Guava's Ints.compare instead of Java7's Integers

Java6 compatibilities
diff --git a/java_gen/pre-written/src/main/java/org/projectfloodlight/openflow/types/U16.java b/java_gen/pre-written/src/main/java/org/projectfloodlight/openflow/types/U16.java
index c52a74a..2f8bfee 100644
--- a/java_gen/pre-written/src/main/java/org/projectfloodlight/openflow/types/U16.java
+++ b/java_gen/pre-written/src/main/java/org/projectfloodlight/openflow/types/U16.java
@@ -22,6 +22,8 @@
 import org.projectfloodlight.openflow.protocol.OFMessageReader;
 import org.projectfloodlight.openflow.protocol.Writeable;
 
+import com.google.common.primitives.Ints;
+
 public class U16 implements Writeable, OFValueType<U16> {
     private final static short ZERO_VAL = 0;
     public final static U16 ZERO = new U16(ZERO_VAL);
@@ -113,6 +115,6 @@
 
     @Override
     public int compareTo(U16 o) {
-        return Integer.compare(f(raw), f(o.raw));
+        return Ints.compare(f(raw), f(o.raw));
     }
 }