NAME
        WaitIO -- wait for completion of an I/O request

   SYNOPSIS
        error = WaitIO(iORequest)
        D0             A1

        byte waitio(struct iorequest *);

   FUNCTION
        This function waits for the specified I/O request to complete, then
        removes it from the replyport.  If the I/O has already completed,
        this function will return immediately.

        This function should be used with care, as it does not return until
        the I/O request completes; if the I/O never completes, this
        function will never return, and your task will hang.  If this
        situation is a possibility, it is safer to use the wait() function.
        wait() will return return when any of a specified set of signal is
        received.  This is how I/O timeouts can be properly handled.

   WARNING
        If this iorequest was "quick" or otherwise finished before this
        call, this function drops though immediately, with no call to
        wait().  a side effect is that the signal bit related the port may
        remain set.  Expect this.

        When removing a known complete iorequest from a port, waitio() is the
        preferred method.  A simple remove() would require a disable/enable
        pair!

   INPUTS
        iORequest - pointer to an I/O request block

   RESULTS
        error - zero if successful, else an error is returned
                (a sign extended copy of io_Error).

   SEE ALSO
        doio(), sendio(), checkio(), abortio()