Apply patch 4636051. COLLADA: Export selection.

Original patch by Jan Diederich, adapted by Pelle Johnsen. Review assistance by Daniel Tavares.

This patch adds an option to export only the selection.

source/blender/collada/DocumentExporter.h

@@ -34,7 +34,7 @@ struct Scene;
 class DocumentExporter
 {
  public:
-	void exportCurrentScene(Scene *sce, const char* filename);
+	void exportCurrentScene(Scene *sce, const char* filename, bool selected);
 	void exportScenes(const char* filename);
 };