- When one does a select on a file descriptor that is meaningless for that particular file type, select shall indicate that the file descriptor is ready for that particular operation and that the file descriptor has no exceptional condition pending.
if the process was REVIVING. (susp_count doesn't count those
processes.) this together with dev_io SELECT suspend side effect
for asynch. character devices solves the hanging pipe bug. or
at last vastly improves it.
added sanity checks, turned off by default.
made the {NOT_,}{SUSPENDING,REVIVING} constants weirder to
help sanity checking.
