The classes ZipEntry, ZipFile, ZipInputStream and ZipOutputStream all
implement ZipConstants, which is a non-public interface.

This means that these internal constants, which exist only for implementation
reasons, are exposed in the public API. The constants have no documentation,
and are not useful to the Java programmer.

Strictly speaking, fixing this bug is an API change. However, it should not
break any real programs. It is likely to break the Conformance test suite
though...

Generally speaking, we should weed out all cases where public classes implement non-public interfaces.

###@###.### 2001-10-08