Allow ~ in file names so libtool droppings in contrib don't break updates.
It has happened twice now, and is likely to happen again.

Errata notice candidate.
Do not error out when adding an interface to a group to which it
already belongs or removing it from a group to which it does not
belong.  This makes it possible to include group memberships in
ifconfig_foo0 in rc.conf without fear of breaking "service netif
restart foo0".

MFC after:	3 days
Last few remnants of BIND (hopefully...)

MFC after:	3 days