make QgsMapLayerRegistry ctor private (it's a singleton)

Author: jef-n

python/core/qgsmaplayerregistry.sip

@@ -213,10 +213,8 @@ class QgsMapLayerRegistry : QObject
      */
     void legendLayersAdded( QList<QgsMapLayer*> theMapLayers );
 
-  protected:
-    //! protected constructor
-    QgsMapLayerRegistry( QObject * parent = 0 );
-
   private:
+    QgsMapLayerRegistry(); // private 'cause it's a singleton
+
     void connectNotify( const char * signal );
 }; // class QgsMapLayerRegistry

src/core/qgsmaplayerregistry.h

@@ -239,15 +239,15 @@ class CORE_EXPORT QgsMapLayerRegistry : public QObject
     void legendLayersAdded( QList<QgsMapLayer*> theMapLayers );
 
   protected:
-    //! protected constructor
-    QgsMapLayerRegistry( QObject * parent = 0 );
-
     /** debugging member
         invoked when a connect() is made to this object
     */
     void connectNotify( const char * signal );
 
   private:
+    //! private singleton constructor
+    QgsMapLayerRegistry( QObject * parent = 0 );
+
     static QgsMapLayerRegistry *mInstance;
     QMap<QString, QgsMapLayer*> mMapLayers;
     QSet<QgsMapLayer*> mOwnedLayers;