Add BitSet#clone

Author: TheLogicMaster

runtime/src/java/util/BitSet.java

@@ -112,6 +112,10 @@ private BitSet(long[] bits, boolean needClear, int actualArrayLength,
         this.isLengthActual = isLengthActual;
     }
 
+    public BitSet clone() {
+        return new BitSet(Arrays.copyOf(bits, bits.length), needClear, actualArrayLength, isLengthActual);
+    }
+
     /**
      * Compares the argument to this {@code BitSet} and returns whether they are
      * equal. The object must be an instance of {@code BitSet} with the same