)
Call the XMS v3.0+ driver "Reallocate upper memory block" function with:
	AH = 12h
	DX = segment address of UMB to resize
	BX = new size of block in paragraphs
Return: AX = status
	    0001h success
	    0000h failure
		BL = error code (80h,B0h,B2h) (see #02775)
		DX = maximum available size (RM386)
Note:	the XMS driver need not implement functions 10h through 12h to be
	  considered compliant with the standard
SeeAlso: #02765,#02766,#02767,#02783