INT 31 P - DPMI 1.0+ - SERIALIZE SHARED MEMORY
        AX = 0D02h
        SI:DI = shared memory block handle
        DX = flags
            bit 0: return immediately rather than suspending if serialization
                        unavailable
                1: shared rather than exclusive serialization
                2-15: reserved (0)
Return: CF clear if successful
        CF set on error
            AX = error code (8004h,8005h,8017h-8019h,8023h) (see AX=0000h)
Notes:  an exclusive serialization blocks any other serialization attempts for
          the same block by another virtual machine; a shared serialization
          blocks attempts at exclusive serialization by another virtual machine
        hosts are not required to detect deadlock
        a client's interrupt handler can cancel a serialization call which
          caused it to block by calling AX=0D03h
SeeAlso: AX=0D03h