java_gen: value types: add NO_MASK, FULL_MASK constants where missing

This is necessary so types can distinguish non-canonical forms.
diff --git a/java_gen/pre-written/src/main/java/org/projectfloodlight/openflow/types/U32.java b/java_gen/pre-written/src/main/java/org/projectfloodlight/openflow/types/U32.java
index 9fafc30..7f53374 100644
--- a/java_gen/pre-written/src/main/java/org/projectfloodlight/openflow/types/U32.java
+++ b/java_gen/pre-written/src/main/java/org/projectfloodlight/openflow/types/U32.java
@@ -29,6 +29,10 @@
     private final static int ZERO_VAL = 0;
     public final static U32 ZERO = new U32(ZERO_VAL);
 
+    private static final int NO_MASK_VAL = 0xFFffFFff;
+    public final static U32 NO_MASK = new U32(NO_MASK_VAL);
+    public static final U32 FULL_MASK = ZERO;
+
     private final int raw;
 
     private U32(int raw) {
@@ -42,6 +46,8 @@
     public static U32 ofRaw(int raw) {
         if(raw == ZERO_VAL)
             return ZERO;
+        if(raw == NO_MASK_VAL)
+            return NO_MASK;
         return new U32(raw);
     }