Cleanup: Drop unused forward declaration (#113)

Signed-off-by: Michael Carroll <[email protected]>

Author: mjcarroll

graphics/include/ignition/common/Animation.hh

@@ -34,7 +34,6 @@ namespace ignition
     class KeyFrame;
     class PoseKeyFrame;
     class NumericKeyFrame;
-    class AnimationPrivate;
     class TrajectoryInfoPrivate;
 
     /// \class Animation Animation.hh ignition/common/Animation.hh

graphics/src/Animation.cc

@@ -40,11 +40,15 @@ namespace
 }
 
 /////////////////////////////////////////////////
-class ignition::common::AnimationPrivate
+namespace ignition {
+namespace common {
+class AnimationPrivate
 {
   /// \brief true if the animation is interpolated in x
   public: bool interpolateX = false;
 };
+}  // namespace ignition
+}  // namespace common
 
 // TODO(luca) Make Animation class follow PIMPL and remove global static map
 /////////////////////////////////////////////////