dnsdist: add package

dnsdist: add package

Maintainer: me
Compile tested: armv7l, OpenWRT SDK
Run tested: armv7l  Linksys WRT1900ACS, OpenWrt SNAPSHOT, r9987-655fff1571 -
confirmed dnsdist links correctly against dependencies and doesn't experience
errors at run-time when enabling features.

Description:
dnsdist is a highly DNS-, DoS- and abuse-aware loadbalancer. Its goal in life is
to route traffic to the best server, delivering top performance to legitimate
users while shunting or blocking abusive traffic.

dnsdist is dynamic, its configuration language is Lua and it can be changed at
runtime, and its statistics can be queried from a console-like interface or an
HTTP API.

https://dnsdist.org/

Closes: PowerDNS/pdns#3294
Signed-off-by: James Taylor <james@jtaylor.id.au>