Adds assertion to verify that pickle/unpickle produces a new object

Author: egalpin

src/test/java/com/fasterxml/jackson/core/TestJsonPointer.java

@@ -259,6 +259,7 @@ public void testPointerSerialization() throws Exception {
         final String INPUT = "/Image/15/name";
         JsonPointer original = JsonPointer.compile(INPUT);
         JsonPointer copy = unpickle(pickle(original), JsonPointer.class);
+        assertNotSame(copy, original);
         assertEquals(original, copy);
 
     }