NAME
        PRead - internal read from printer port

   SYNOPSIS
        error = (*PrinterData->pd_PRead)(buffer, length, tv);
        D0

        long pread(ubyte *, ulong *, struct timeval *);

   FUNCTION
        PRead reads a buffer of data from the printer port. The variable
        length points to is set to the actual number of read bytes.

        tv points to a struct timeval or is null in which case the default
        time is PrinterExtendedData.ped_TimeoutSecs. If the time of tv
        ellapes before the cmd_read at the printer port is done two different
        things may happen: If at least one char is read PRead() returns. If
        no char is read but pquery returns a value larger 0 the read is
        repeated with that length to read all outstanding data.