Implement torrent synchronization and automatic notification on torrent alerts

[joriscarrier]

No description provided.

[arvidn]

what's the rationale for this change? it's not obvious from the documentation you added.
it looks like you also meant to expose the wait functions to torrent_handle as well, otherwise they're not usable by the client.

But more fundamentally, I believe this kind of mechanism would be implemented either by a plugin or by a set_alert_notify() function. It's not obvious why this would need to be built into libtorrent.

[arvidn]

if you want a hook on when a torrent changes state, it would probably be better to do something in torrent::set_state(). Going via the alert mechanism won't work if the client clear the alert_category::status bit in the alert mask.

[arvidn]

I also think there's a race condition in here. For example, if you call handle.status() followed by handle.wait(), it the torrent may have changed status before you call wait()