net: use /etc/hosts first when looking up IP addresses using native Go's dns resolver
net: use /etc/hosts first when looking up IP addresses using native Go's dns resolver

Previously /etc/hosts would be ignored altogether, this change returns matching results
from that file without talking to a DNS server.

R=rsc
CC=golang-dev
http://codereview.appspot.com/5061042

Committer: Russ Cox <5ad239cb8a44f659eaaee0aa1ea5b94947abe557@golang.org>

wesolows/golang-old,wesolows/golang,wesolows/golang-old,wesolows/golang-old,firebitsbr/golang-old,wesolows/golang-old,wesolows/golang,wesolows/golang-old,firebitsbr/golang-old,wesolows/golang,wesolows/golang,wesolows/golang,firebitsbr/golang-old,firebitsbr/golang-old,wesolows/golang,wesolows/golang-old,wesolows/golang,wesolows/golang-old,firebitsbr/golang-old,firebitsbr/golang-old,firebitsbr/golang-old,firebitsbr/golang-old