INT 61 - Banyan VINES - GET NETWORK DRIVE MAP                                   
	AX = 0004h subfn 0003h
	DS:DX -> request block (see #03404)
Return: AX = status
	    0000h drive map returned in request block
Desc:	Returns a bit map indicating which drive numbers are connected to a
	  file service
Note:	Only bits 0-25 are significant
SeeAlso: AX=0004h/SF=0002h


Format of VINES Function 0004h/Subfunction 0003h request block:
Offset	Size	Description	(Table 03404)
 00h	WORD	0003h
 02h	DWORDDoubleword; four bytes.	 Commonly used to hold a 32-bit segment:offset or selector:offset address.	buffer for drive map (bit0=A, bit1=B, ...)