[Vortex] Auto-discard notification

[Francis Brosnan Blazquez]

Hi Amiaux,

Regarding to the test provided, it is not a bug but missing
documentation. I've updated the vortex_listener_new/2/_full functions
documentation to include some information about the reference returned
and how to close a listener. Here is the information:

--
NOTE: the reference returned is only owned by the vortex engine. This is
not the case of vortex_connection_new where the caller acquires
automatically a reference to the connection (as well as the vortex
engine).

In this case, if your intention is to keep a reference for later
operations, you must call to vortex_connection_ref to avoid losing the
reference if the system drops the connection. In the same direction, you
can't call to vortex_connection_close if you don't own the reference
returned by this function.

To close immediately a listener you can use vortex_connection_shutdown. 
--

Thanks for reporting, Cheers!
-- 
Francis Brosnan Blazquez <francis at aspl.es>
Advanced Software Production Line, S.L.