Allows to store a pair key/value associated to the channel, with optional destroy handlers.
This allows to associate application data to the channel which can be easily retrieved later using vortex_channel_get_data.
The function allows to configure the set of destroy handlers to be called to dealloc key and value stored.
In the case a NULL reference is passed to the function as the value parameter, the pair key/value is removed from the channel, calling to associated destroy functions.
NOTE: the function do not allows storing NULL value pointers.