Add a test to ensure TreeMap's (de)serialization compatibility with OpenJDK

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Make ArrayList's serialization compatible with OpenJDK's

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Mark java.lang.Number as serializable

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Serialize test: augment the hexdump with address and ASCII dump

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>