INT 21 - Novell NetWare - DIRECTORY SERVICES - GET DIRECTORY HANDLE             
	AX = E900h
	DX = drive number to check (0 = A:, ..., 25 = Z:, 26 ... 31)
Return: AL = directory handle
	AH = flags (drive not mapped if none set)
	    bit 0: permanent handle
	    bit 1: temporary handle
	    bit 7: mapped to local drive
Note:	this function is supported by NetWare 4.0+, Advanced NetWare 1.0+, and
	  Alloy NTNX
SeeAlso: AH=E2h/SF=00h,AH=E2h/SF=01h,AH=E2h/SF=0Ah