INT 21 - Novell NetWare - SYNCHRONIZATION SERVICES - EXAMINE SEMAPHORE
        AX = C501h
        CX:DX = semaphore handle
Return: AL = status
            00h successful
                CX = semaphore value (-127 to 127)
                DL = count of processes which have the semaphore open
            FFh invalid handle
Note:   this function is supported by NetWare 4.6+, Advanced NetWare 1.0+, and
          Alloy NTNX
SeeAlso: AX=C502h,AX=C504h