void silc_client_lock_client(SilcClientEntry client_entry);

    Acquires lock for the client entry indicate by `client_entry'.  When
    application wants to access `client_entry' it must lock the entry
    before reading any data from the `client_entry'.  The lock must be
    unlocked with silc_client_unlock_client.

    The entry must be unlocked before calling any Client Library API
    functions where the entry is given as argument, unless otherwise stated.

    The entry should not be locked for long periods of time.  For example,
    it is not appropriate to hold the lock while waiting user interface to
    be drawn.  The appropriate way is to read the data and duplicate it if
    necessary, unlock the entry, then draw on the user interface.

    This function is not needed if application is not multithreaded.