dnsmasq: steal resolvconf support from Ubuntu

Add support for resolvconf integration as done in Ubuntu. This implies
updates of start-scripts, resolvconf plugin (on nameserver update ...),
populate-volatiles control file for saved nameserver list.

Signed-off-by: Jens Rehsack <sno@netbsd.org>
Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>
Signed-off-by: Joe MacDonald <joe_macdonald@mentor.com>