Represents something akin to a sleep() call that can be interrupted.
You create this datum, give a copy to some other place and call
wait() to sleep until interrupted.
The other place can then call
INTERRUPT_SLEEP(the_isleep) to wake up the sleep.
|wait||Sleep until interrupted.|
Sleep until interrupted.
@param isleep How long to wait. If not provided sleep indefinitely. @return TRUE if interrupted, FALSE if not.