[package] add pdnsd DNS proxy

[package] add pdnsd DNS proxy

pdnsd, is an IPv6 capable proxy DNS server with permanent caching (the cache
contents are written to hard disk on exit) that is designed to cope with
unreachable or down DNS servers (for example in dial-in networking).

pdnsd can be used with applications that do dns lookups, eg on startup, and
can't be configured to change that behaviour, to prevent the often
minute-long hangs (or even crashes) that result from stalled dns queries.

Signed-off-by: Sebastian Muszynski <basti@linkt.de>
git-svn-id: svn://svn.openwrt.org/openwrt/packages@33173 3c298f89-4303-0410-b956-a3cf2f4a3e73