[package] ppp:

[package] ppp:
	- don't let pppd control resolv.conf.auto because it will wipe foreign dns entries
	- handle dns setup in ip-up handler
	- use add_dns() and remove_dns() to only add/remove dns entries related to the corresponding pppd instance
	- make pppd shutdown work for interfaces without ifname option, e.g. pptp

git-svn-id: svn://svn.openwrt.org/openwrt/trunk@21392 3c298f89-4303-0410-b956-a3cf2f4a3e73