Audio: don't use `using` when not needed.

It's a PITA when porting to compatibility branch (too many
annoying issues with MSVC 2013 and GCC 4.6).

src/Magnum/Audio/Audio.h

@@ -42,16 +42,16 @@ class Source;
 #endif
 
 template<UnsignedInt> class Playable;
-using Playable2D = Playable<2>;
+typedef Playable<2> Playable2D;
-using Playable3D = Playable<3>;
+typedef Playable<3> Playable3D;
 
 template<UnsignedInt> class PlayableGroup;
-using PlayableGroup2D = PlayableGroup<2>;
+typedef PlayableGroup<2> PlayableGroup2D;
-using PlayableGroup3D = PlayableGroup<3>;
+typedef PlayableGroup<3> PlayableGroup3D;
 
 template<UnsignedInt> class Listener;
-using Listener2D = Listener<2>;
+typedef Listener<2> Listener2D;
-using Listener3D = Listener<3>;
+typedef Listener<3> Listener3D;
 
 }}
 

src/Magnum/Audio/Listener.h

@@ -197,14 +197,14 @@ template <UnsignedInt dimensions> class Listener: public SceneGraph::AbstractFea
  *
  * @see @ref Listener3D
  */
-using Listener2D = Listener<2>;
+typedef Listener<2> Listener2D;
 
 /**
  * @brief Listener for three dimensional float scenes
  *
  * @see @ref Listener2D
  */
-using Listener3D = Listener<3>;
+typedef Listener<3> Listener3D;
 
 #if defined(CORRADE_TARGET_WINDOWS) && !defined(__MINGW32__)
 extern template class MAGNUM_AUDIO_EXPORT Listener<2>;

src/Magnum/Audio/Playable.h

@@ -173,6 +173,7 @@ template<UnsignedInt dimensions> class Playable: public SceneGraph::AbstractGrou
  * @see @ref Playable3D
  */
 typedef Playable<2> Playable2D;
+
 /**
  * @brief Playable for three dimensional float scenes
  *

src/Magnum/Audio/PlayableGroup.h

@@ -199,14 +199,14 @@ template<UnsignedInt dimensions> inline void PlayableGroup<dimensions>::setClean
  *
  * @see @ref PlayableGroup3D
  */
-using PlayableGroup2D = PlayableGroup<2>;
+typedef PlayableGroup<2> PlayableGroup2D;
 
 /**
  * @brief Playable group for three dimensional float scenes
  *
  * @see @ref PlayableGroup2D
  */
-using PlayableGroup3D = PlayableGroup<3>;
+typedef PlayableGroup<3> PlayableGroup3D;
 
 }}