ping_iterator_set_context can be used to store host-specific data within the
liboping structures. This data can be received again by calling
ping_iterator_get_context. The data itself is never touched by liboping. If
you call ping_host_remove (see ping_host_add(3)) or ping_destroy (see
ping_construct(3)) and the context is not NULL liboping will assume you know
what you're doing and simply ignore the fact this might be a memory leak.
The iter argument is an iterator object as returned by
ping_iterator_get(3) and ping_iterator_next.
The context argument of ping_iterator_set_context is a pointer to
anything and may be NULL.
ping_iterator_get_context returns the same pointer previously passed to
ping_iterator_set_context or NULL if ping_iterator_set_context has never
been called before.