one are running in the pool, it will be
significantly broken so it is not usually worth troubling about this -
the program is doomed in that event whatever.  However if that is
wrong and the cause of the failure to start any threads can be
addressed, then the thread pool can be brought back into use by
calling this procedure again with a positive value (which can be
preceded by a call with a negative value to prevent too many threads
trying to start).
</p>
<p>This procedure is first available in version 0.1