No `using namespace std` anywhere.

Remains from the dark old times.

src/SceneGraph/AbstractCamera.hpp

@@ -32,8 +32,6 @@
 
 #include "Drawable.h"
 
-using namespace std;
-
 namespace Magnum { namespace SceneGraph {
 
 namespace Implementation {

src/SceneGraph/Camera2D.hpp

@@ -31,8 +31,6 @@
 #include "AbstractCamera.hpp"
 #include "Camera2D.h"
 
-using namespace std;
-
 /** @todo Use AbstractBasicCamera2D<T> when support for GCC 4.6 is dropped (also in header) */
 
 namespace Magnum { namespace SceneGraph {