INT 2C P - Cloaking - GET BASE ADDRESS OF GDT SELECTOR                          
	AX = 000Ah
	SI = selector
Return: CF clear if successful
	    EBX = segment base address
	CF set on error
	    AX = error code (see #02556)
Note:	this function was first introduced with RM386 (RAM-MAN/386) v6.00, the
	  memory manager included in Helix Software's Netroom
SeeAlso: AX=0000h,AX=0002h,AX=000Bh