astutil: move to go/ast/astutil

Change-Id: I9a45bfc07613eb2210081d306d71f0a4d152eda5
Reviewed-on: https://go-review.googlesource.com/2592
Reviewed-by: Alan Donovan <adonovan@google.com>
diff --git a/go/loader/loader.go b/go/loader/loader.go
index c568ea2..ad7e14d 100644
--- a/go/loader/loader.go
+++ b/go/loader/loader.go
@@ -136,7 +136,7 @@
 	"os"
 	"strings"
 
-	"golang.org/x/tools/astutil"
+	"golang.org/x/tools/go/ast/astutil"
 	"golang.org/x/tools/go/gcimporter"
 	"golang.org/x/tools/go/types"
 )