Include what you use for the preparser.

src/fast-dtoa.h

Index: src/fast-dtoa.h
diff --git a/src/fast-dtoa.h b/src/fast-dtoa.h
index ef285579341616a495ebf0c1c2ad08b9a92512fe..6469e2d778ac9bc8be27eb593e95229095600ed5 100644
--- a/src/fast-dtoa.h
+++ b/src/fast-dtoa.h
@@ -1,4 +1,4 @@
-// Copyright 2011 the V8 project authors. All rights reserved.
+// Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
@@ -31,6 +31,8 @@
 namespace v8 {
 namespace internal {
 
+template <typename T> class Vector;
+
 enum FastDtoaMode {
   // Computes the shortest representation of the given input. The returned
   // result will be the most accurate number of this length. Longer