QmlJS: Adjust existing code for updated QML parser.

Change-Id: I153723eeb9973be025daf47e317f7b9d076a3c72
Reviewed-on: http://codereview.qt-project.org/4733
Reviewed-by: Thomas Hartmann <Thomas.Hartmann@nokia.com>

src/libs/qmljs/qmljsdocument.h

@@ -112,7 +112,6 @@ private:
 
 private:
     QmlJS::Engine *_engine;
-    NodePool *_pool;
     AST::Node *_ast;
     Bind *_bind;
     QList<QmlJS::DiagnosticMessage> _diagnosticMessages;