void silc_cond_signal(SilcCond cond);

    Signals a waiting thread and wakes it up.  If there are no waiters
    this function has no effect.  In case of multiple waiters only one
    is signalled.  To signal all of them use silc_cond_broadcast.

    Before calling this function the mutex used with the silc_cond_wait
    must be acquired.

    silc_mutex_lock(lock);
    c->a = context;
    silc_cond_signal(cond);
    silc_mutex_unlock(lock);