INT E0 - DR Multiuser DOS - "A_ATTACH" - ATTACH AUX DEVICE
	CL = A5h
Return: nothing (DR)
	AX = status (REAL/32)
Desc:	attaches the default auxiliary device to the calling process unless
	  it is already attached to another process, in which case the call
	  blocks until the device becomes available
Notes:	this call should be used before attempting to read or write from
	  the AUX device; however, the I/O calls internally call this function
	  to ensure device ownership
	also supported by REAL/32
SeeAlso: INT E0/CL=03h,INT E0/CL=04h,INT E0/CL=A6h,INT E0/CL=A7h,INT E0/CL=A8h
SeeAlso: INT E0/CL=ACh,INT E0/CL=ADh,INT E0/CL=B0h