Int 2Fh / 4B04h         Free Switcher ID                             DOS 5.0+

    Frees the switcher identifier associated with the task switcher
    having the specified service-function handler. When a task
    switcher terminates, it calls this function.

    Client programs must not call this function.

        Entry   AX    = 4B04h
                BX    = ID (allocated by Int 2Fh function 4B03h)
                ES:DI = Address of service-function handler

        Return  AX = BX = 00h   Success
                or
                BX > 0          Invalid switcher ID

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