Convert smcroute to use the elegant libev instead of home grown poll() etc.

This commit converts all home grown event handling to use libev instead.
For information on libev, see http://software.schmorp.de/pkg/libev.html

Please note that no IPv6 code paths have been tested in this commit,
only IPv4 multicast group join and routing.

Signed-off-by: Jonas Johansson <jonasj76@gmail.com>
Signed-off-by: Joachim Nilsson <troglobit@gmail.com>