INT 31 - DPMI 0.9+ - FREE DOS MEMORY BLOCK

	AX = 0101h
	DX = selector of block
Return: CF set if successful
	CF set on error
	    AX = DOS error code (07h,09h) (see #01680 at INT 21/AH=59h/BX=0000h)
Notes:	all descriptors allocated for the block are automatically freed
	DPMI 1.0+ automatically zeros any segment registers containing a
	  selector freed by this function
	not supported by MS Windows 3.0 in Standard mode
SeeAlso: AX=0100h,AX=0102h,AX=0502h