bug #50008: Incorrect logging of nsfileid and nshost

Added the following template function to the Dlf client API so that clients
can specify the CASTOR file id and name server host as the context for a DLF
message whilst also being able to specify the parameters as an array which the
C++ ifunction template mechanism will automatically determine the size of in
order to avoid potential segmentation faults.

    template<int numparams>
    void dlf_writep (Cuuid_t uuid,
                     int severity,
                     int message_no,
                     u_signed64 fileId,
                     std::string nsHost,
                     castor::dlf::Param (&params)[numparams]) throw() {
      dlf_writep(uuid, severity, message_no, fileId, nsHost, numparams,
        params);
    }