tm-hppa64.h defines a GDB_TARGET_IS_HPPA_20W flag that needs to go. Most 
of the uses of this flag have been cleaned up already; there's only one 
left in hppa-hpux-tdep.c that is cleaned up by this patch. Once that is 
done, we can get rid of tm-hppa64.h

Thoughts? Comments?

randolph