Change freezer to skip copying specific types

* The previous code skipped freezing and copying, when in fact it is
  still valid to freeze some kinds of objects, but not dup them.
* This is probably not ready because I think @mbj will want to
  object to having Class and Module frozen like this. We will need
  to come up with a solution, whether it's something specific to
  Adamantium or even in IceNine, I'm not sure. Although I assume the
  former, since I'm not sure if it'd be a good idea to have IceNine
  skip freezing Class and Module instances globally since there are
  valid use cases where you would want this to happen.