SMACK-428 add 'public int RosterEntry.hashCode()'

git-svn-id: http://svn.igniterealtime.org/svn/repos/smack/branches/smack_3_3_1@13662 b35dd754-fafc-0310-a699-88a17e54d16e

source/org/jivesoftware/smack/RosterEntry.java

@@ -181,6 +181,11 @@ public class RosterEntry {
         }
     }
 
+    @Override
+    public int hashCode() {
+        return this.user.hashCode();
+    }
+
     /**
      * Indicates whether some other object is "equal to" this by comparing all members.
      * <p>