Prevent CCEs in `Entry.equals` with non-`Entry` args

It's possible for an `Entry` to end up in, for example, a `Set<Object>`, where it will be compared for equality with other objects that are neither `Entry` nor derived from it. The general contract for `Object.equals(Object)` demands that `Entry` return `false` in this case, rather than raising an exception.

I ran into this with, of all things, Jersey declarative link generation, which recursed into something that contained a `ClassLoader` reference, which in turn pointed to the Maven classloader. Very much an edge case, but for me it's a showstopping one.