check the new events before calling epoll_ctl.
Assume tel phone is voice phone

This allow Jitsi client to make SIP calls
Merge pull request #25 from Pitel/XEP-0054

Assume tel phone is voice phone
Merge pull request #24 from fanyunfeng/master

Shortcut unnecessary epoll_ctl calls. Save the events in priv_fd->events then check the value before reset the events of fd.