Availability:C-language interface function
int PL_handle_signals(void)Handle any signals pending from PL_raise(). PL_handle_signals() 
is called at each pass through the call- and redo-port at a safe point. 
Exceptions raised by the handler using PL_raise_exception() 
are properly passed to the environment.
The user may call this function inside long-running foreign functions 
to handle scheduled interrupts. This routine returns the number of 
signals handled. If a handler raises an exception, the return value is 
-1 and the calling routine should return with FALSE as soon 
as possible.