Added initializer

git-svn-id: http://svn.openscenegraph.org/osg/OpenSceneGraph/branches/OpenSceneGraph-3.4@15113 16af8721-9629-0410-8352-f15c8da7e697

include/osg/State

@@ -1592,7 +1592,8 @@ class OSG_EXPORT State : public Referenced
         {
             typedef std::vector<StateSet::DefinePair> DefineVec;
 
-            DefineStack() {}
+            DefineStack():
+                changed(false) {}
 
             void print(std::ostream& fout) const;