[dns64] adds an access control list to dns config (#203)
[dns64] adds an access control list to dns config (#203)

Adds the `thread` acl to restrict queries (recursive and not) to the
local thread network. Fixes #181
openthread/borderrouter,openthread/ot-br-posix,bukepo/borderrouter,openthread/ot-br-posix,openthread/borderrouter,bukepo/borderrouter,jwhui/borderrouter,bukepo/borderrouter,jwhui/borderrouter,openthread/borderrouter,jwhui/borderrouter,jwhui/borderrouter,openthread/borderrouter,openthread/ot-br-posix,bukepo/borderrouter,bukepo/borderrouter,jwhui/borderrouter,openthread/ot-br-posix,openthread/borderrouter,openthread/ot-br-posix,openthread/borderrouter,openthread/ot-br-posix