INT 31 P - DPMI 0.9+ - FREE MEMORY BLOCK
        AX = 0502h
        SI:DI = handle of memory block
Return: CF clear if successful
        CF set on error
            AX = error code (DPMI 1.0+) (8023h) (see AX=0000h)
Note:   any selectors allocated for the memory block must also be freed,
          preferably before freeing the memory block
SeeAlso: AX=0101h,AX=0501h,AX=0D01h