[CTX] [ALL] Host name resolution

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Host name resolution

Resolve host name to/from IP address using DNS, NIS or local file.

--	----------	------------------	----------------------------------
*	HOSTS	host/addr,...	private host/address mapping
	RESOLV	file,nis,dns,sys	the order of resolvers to be used
	RES_WAIT	sec:host	wait for resolver to be ready
	RES_CONF	URL	where resolv.conf is
	RES_NS	host[:port]	DNS server to be used
	RES_AF	46 | 64 | 4 | 6	Address families (IPv4/v6) to be retrieved
	RES_RR	HostList	enable Round Robin of IP-addresses
	RES_VRFY	""	enable double check of reverse resolution
	RES_DEBUG	number	debugging level of name resolution

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