INT E0 - DR Multiuser DOS - "A_READBLK" - READ STRING FROM AUX DEVICE

	CL = ACh
	DS:DX -> character control block (CHCB) (see #04051,#04052)
Return: AX = number of characters read
Desc:	read characters from the default auxiliary (AUXn:) device into a buffer
	  until the buffer is full or the device is no longer ready
Notes:	if the device is initially not ready, blocks until at least one
	  character has been read
	if another process owns AUX, this call blocks until the device becomes
	  available
	also supported by REAL/32
SeeAlso: INT E0/CL=03h,INT E0/CL=A5h,INT E0/CL=ADh