DERBY-4741 improves Derby's handling of interrupts. Now the engine
does not fall over when an interrupt occurs. Instead, Derby only kills
the connection which is running when the interrupt happens, which may
also be useful to stop execution in certain situations. Other times
the connection will survive, i.e. the interrupt is ignored by Derby,
although the interrupt status flag is kept. The exact behavior has
been discussed on
DERBY-4741 from 2011-02-10 onward.