[master] ECS authoritative support

[master] ECS authoritative support

3936.	[func]		Added authoritative support for the EDNS Client
			Subnet (ECS) option.

			ACLs can now include "ecs" elements which specify
			an address or network prefix; if an ECS option is
			included in a DNS query, then the address encoded
			in the option will be matched against "ecs" ACL
			elements.

			Also, if an ECS address is included in a query,
			then it will be used instead of the client source
			address when matching "geoip" ACL elements.  This
			behavior can be overridden with "geoip-use-ecs no;".

			When "ecs" or "geoip" ACL elements are used to
			select a view for a query, the response will include
			an ECS option to indicate which client network the
			answer is valid for.

			(Thanks to Vincent Bernat.) [RT #36781]