Modifies the Filters attribute of a given X25 Server Client
    instance to include at least the specified filter or filters.

    add  [node node-id] x25 server client simple-name -
         filters {simplename[,simplename...]}

    Filters

    Default: No default    Value: Set of simple names

    Set of filters to be used by the server to filter calls for
    this X.25 client. Each name is the name of an x25 access filter
    entity.