INT 2A CU - NETWORK - END DOS CRITICAL SECTION
        AH = 81h
        AL = critical section number (00h-0Fh) (see AH=80h)
Notes:  normally hooked rather than called
        the handler should reawaken any tasks which were suspended due to an
          attempt to enter the specified critical section
SeeAlso: AH=80h,AH=82h,AX=8700h

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