INT 31 - DPMI 0.9+ - SET DESCRIPTOR

	AX = 000Ch
	BX = LDT selector
	ES:(E)DI -> 8-byte buffer containing descriptor
Return: CF clear if successful
	CF set on error
	    AX = error code (DPMI 1.0+) (8021h,8022h,8025h) (see #03143)
Notes:	16-bit programs use ES:DI as pointer, 32-bit must use ES:EDI
	only modify descriptors allocated with INT 31/AX=0000h
	DPMI 1.0+ automatically reloads any segment registers containing the
	  selector being modified
	not supported by MS Windows 3.0 in Standard mode
SeeAlso: AX=000Bh