Polling on file descriptors / external sockets not supported in active_poller

[stephanschim]

Polling on file descriptors / external sockets is not supported in active_poller.
There is basic support in poller_t now (only add function), but not in active_poller.

[stephanschim]

I have a patch for this, but how can I submit it?

[stephanschim]

stephanschim#1

[stephanschim]

#606