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.