Serializers for unmodifiable Java collections.

[chermenin]

Added serializers for collections created via
Collections.unmodifiable...() and Collections.empty...() methods.

[johnynek]

these are all basically the same. Can we share the code? Something like:

public abstract class UnmodifiableJavaCollectionSerializer<T, U> extends Serializer<T> {
    protected U getInner(T t);
    protected T build(U u);

    @Override
    public Collection<?> read(Kryo kryo, Input input, Class<T> type) {
        try {
            U c = (U) kryo.readClassAndObject(input);
            return build(c);
        } catch (Exception e) {
            throw new RuntimeException(e);
        }
    }

    @Override
    public void write(Kryo kryo, Output output, T object) {
        try {
            U c = getInner(object);
            kryo.writeClassAndObject(output, c);
        } catch (RuntimeException e) {
            // Don't eat and wrap RuntimeExceptions because the ObjectBuffer.write...
            // handles SerializationException specifically (resizing the buffer)...
            throw e;
        } catch (Exception e) {
            throw new RuntimeException(e);
        }
    }
}

Then we can just implement the code to read the inner and wrap for each of them.

Also, could you possibly set your editor to 2 space indent, which is the style we use?

[chermenin]

Great thought! Thanks for review.