initial stab at 'ALIAS' or 'ANAME' records for PowerDNS. To use, set an ALIAS record on your apex. Secondly, configure PowerDNS with 'recursor=a.recursor.ip'. Sample zone:

@	IN	SOA	ns1 ahu 2014091619 7200 3600 1209600 3600
@	IN	NS	ns1
@	IN	NS	ns2
www	IN	CNAME	xs.powerdns.com.
ns1	IN	A	1.2.3.4
ns2	IN	A	4.3.2.1
@	IN	ALIAS	www.powerdns.com.
@	IN	MX	25 outpost.ds9a.nl.
elsewhere	IN	CNAME	@

Semantics are that real records override the ALIAS. We only reach out to the alias record if nothing else matched.
this currently breaks ANY queries for the apex btw.
some documentation
remove spurious 'any' (thanks seth) plus clarify CNAME walking
typos
EDNS0, AXFR details, rationale, some wording improvements
Merge branch 'master' into alias

Conflicts:
	pdns/dnsproxy.cc
Merge branch 'alias'