Problem with Throwable in the class table

When Throwable is written in the class table, it causes a problem between JDK 6 and 7 because there is a new field in Throwable added in 7. Because the descriptor does not come over, that information is lost.

Either we need a separate ClassTable entry for JDK 6 vs JDK 7 Throwable (with clever conversion logic therein), or we need to stop sending the ClassTable code for Throwable and start just writing the Throwable natively (we must still support reading the code for compat though).