go.tools: use golang.org/x/... import paths

Rewrite performed with this command:
  sed -i '' 's_code.google.com/p/go\._golang.org/x/_g' \
    $(grep -lr 'code.google.com/p/go.' *)

LGTM=rsc
R=rsc
CC=golang-codereviews
https://golang.org/cl/170920043
diff --git a/godoc/server.go b/godoc/server.go
index 5923b79..7963cd0 100644
--- a/godoc/server.go
+++ b/godoc/server.go
@@ -27,9 +27,9 @@
 	"text/template"
 	"time"
 
-	"code.google.com/p/go.tools/godoc/analysis"
-	"code.google.com/p/go.tools/godoc/util"
-	"code.google.com/p/go.tools/godoc/vfs"
+	"golang.org/x/tools/godoc/analysis"
+	"golang.org/x/tools/godoc/util"
+	"golang.org/x/tools/godoc/vfs"
 )
 
 // handlerServer is a migration from an old godoc http Handler type.