cache parsed pri & prf files

no point in re-parsing them over and over during the scan of a bigger
project ...

shaves off another 20% of the loading time of Qt 4.6.

src/plugins/qt4projectmanager/qt4projectmanagerplugin.cpp

@@ -169,6 +169,8 @@ bool Qt4ProjectManagerPlugin::initialize(const QStringList &arguments, QString *
     addAutoReleasedObject(MaemoManager::instance());
 #endif
 
+    new ProFileCacheManager(this);
+
     // TODO reenable
     //m_embeddedPropertiesPage = new EmbeddedPropertiesPage;
     //addObject(m_embeddedPropertiesPage);