net: parse aliases in /etc/hosts correctly

Previous behaviour only picked the first entry (official hostname) but not the aliases.

R=rsc
CC=golang-dev
https://golang.org/cl/193092

src/pkg/net/hosts.go

@@ -40,10 +40,12 @@ func readHosts() {
 			if len(f) < 2 || ParseIP(f[0]) == nil {
 				continue
 			}
-			h := f[1]
+			for i := 1; i < len(f); i++ {
+				h := f[i]
 				old, _ := hs[h]
 				hs[h] = appendHost(old, f[0])
 			}
+		}
 		// Update the data cache.
 		hosts.time, _, _ = os.Time()
 		hosts.path = hp

src/pkg/net/hosts_test.go

@@ -24,6 +24,12 @@ var hosttests = []hostTest{
 		IPv4(127, 1, 1, 1),
 	}},
 	hostTest{"loki", []IP{}},
+	hostTest{"ullr", []IP{
+		IPv4(127, 1, 1, 2),
+	}},
+	hostTest{"ullrhost", []IP{
+		IPv4(127, 1, 1, 2),
+	}},
 }
 
 func TestLookupStaticHost(t *testing.T) {

src/pkg/net/hosts_testdata

@@ -3,6 +3,8 @@
 127.0.0.3	odin  # inline comment 
 ::2             odin
 127.1.1.1	thor
+# aliases
+127.1.1.2	ullr ullrhost
 # Bogus entries that must be ignored.
 123.123.123	loki
 321.321.321.321