Made predata smaller by storing symbol data in variable length base-128.

src/utils.h

Index: src/utils.h
diff --git a/src/utils.h b/src/utils.h
index d605891e6debb5b9e6c8c68b599a5d98987e8296..fefbfe9af6e36bd0ff56fd1e6cef3a62951b08f6 100644
--- a/src/utils.h
+++ b/src/utils.h
@@ -391,6 +391,12 @@ class Vector {
   // Factory method for creating empty vectors.
   static Vector<T> empty() { return Vector<T>(NULL, 0); }
 
+  template<typename S>
+  static Vector<T> cast(Vector<S> input) {
+    return Vector<T>(reinterpret_cast<T*>(input.start()),
+                     input.length() * sizeof(S) / sizeof(T));
+  }
+
  protected:
   void set_start(T* start) { start_ = start; }