Timely destruction and TRACE_SYSTEM_AREAS

[Leopold Toetsch]

t/pmc/io_2 is failing on some tinderboxen that don't have memalign and 
therefore don't have ARENA_DOD_FLAGS set. Besides the wrong count of DOD 
runs, the primary problem is:

The ParrotIO object is found to be alive in some system areas (probably 
processor registers). Due to the conservative approach of the DOD 
strategy this always might happen.

I think, we have a problem.

leo