net: rearrange source files so we could run more tests on windows

R=rsc
CC=golang-dev
https://golang.org/cl/4603043

src/pkg/net/net_test.go

@@ -7,7 +7,6 @@ package net
 import (
 	"flag"
 	"regexp"
-	"runtime"
 	"testing"
 )
 
@@ -103,9 +102,6 @@ var revAddrTests = []struct {
 }
 
 func TestReverseAddress(t *testing.T) {
-	if runtime.GOOS == "windows" {
-		return
-	}
 	for i, tt := range revAddrTests {
 		a, e := reverseaddr(tt.Addr)
 		if len(tt.ErrPrefix) > 0 && e == nil {