Correct buffer size to fix memory corruption

The analysis in eclipse-openj9/openj9#5696 shows that there
is a out of bounds access that is fixed by increasing
the buffer size by 8.  Validated by having the VM
increase all unsafe allocates by 8 and the problem
no longer occurs.

fixes: kohsuke#79

Signed-off-by: Dan Heidinga <daniel_heidinga@ca.ibm.com>

runtime/src/main/java/com4j/Variant.java

@@ -360,10 +360,10 @@ public int comEnumValue() {
      * Creates an empty {@link Variant}.
      */
     public Variant() {
-        image = ByteBuffer.allocateDirect(16);
+        image = ByteBuffer.allocateDirect(24);
         image.order(ByteOrder.LITTLE_ENDIAN);
         // The initial content of a buffer is, in general, undefined. See the documentation of java.nio.Buffer.
-        byte[] b = new byte[16]; // this initializes the array with zeros
+        byte[] b = new byte[24]; // this initializes the array with zeros
         image.put(b); // this prints the zeros to the buffer to guarantee, that the buffer is initialized with zeros.
         image.position(0);
     }