INT E0 - REAL/32 - "L_CATTACH" - CONDITIONALLY ATTACH TO DEFAULT LIST DEVICE
	CL = A1h
Return: AX = status (00h = successful, FFh = unable to attach)
	may destroy SI,DI
Desc:	attach the default list device to the calling process only if it is
	  currently available
SeeAlso: INT E0/CL=92h,INT E0/CL=9Eh,INT E0/CL=A0h