[Vala] Socket source

[Andy Lees <andrewl oz gmail com>]

Hi,

After 0.30, the socket create source function changed from returning a
SocketSource to returning a GLib.Source.  Now, for the correct operation of
the socket callback, the returned object must be a SocketSource, so:

   - Is the implementation still the same, and presumably if so it is safe
   to do a hard cast to a SocketSource on the return object?  That appears to
   be the only option given that SocketSource is a compact class.
   - Why was the change to the return type from socket create_source made?

Regards,

Andrew Lees