Configure: fix broken plugins path on previous contributor patch

Signed-off-by: Eduardo Silva <edsiper@gmail.com>
Epoll: Fix not catched peer close after events modifications (EPOLLRDHUP)

If a socket created on the event loop did some events modifications and
the peer closed the connection, the core did not trap this event. This
patch re-enable the EPOLLRDHUP flag.

Signed-off-by: Eduardo Silva <edsiper@gmail.com>
Configure: New option --upgrade added