Add vectorized implementation for VectorMask.eq()

Currently "VectorMask.eq" is not vectorized:
     public VectorMask<E> eq(VectorMask<E> m) {
        // FIXME: Generate good code here.
        return bOp(m, (i, a, b) -> a == b);
    }

This can be implemented with calling the "xor(m.not())" instead. Since "xor()/not()" have been intrinsified that can be vectorized in hotspot, directly calling them can make this function be vectorized as well.