Fix enum field add/remove

[liuzhengyang]

The private static field in Enum class, in jdk8 and jdk11, is $VALUES, instead of ENUM$VALUES.

I create a pull request #444 to resolve this problem.

And update this change, add/remove enum field is available.

By the way, i can't run tests in ClassInitTest like testEnumAddRemove, these test methods are @ignored, maybe exist some others problems.

[skybber]

I've updated 1.4.2-SNAPSHOT release + added a note about this fix. Thanks.