Deprecated.mixin constructor

Creates an annotation which deprecates mixing in a class.

The annotation can be used on class declarations which can currently be mixed in, so they are marked mixin, but where the ability to mix in will be removed in a later release.

Any existing class declaration which mixes in the annotated class will cause a warning that such use is deprecated. Does not affect classes which extend or implement the annotated class (see Deprecated.extend, Deprecated.implement and Deprecated.subclass).

The message, if given, is displayed as part of the warning. The message should be aimed at the programmer who owns the class which mixes in the annotated class, and should recommend an alternative (if available), and say when this functionality is expected to be removed if that is sooner or later than the next major version.