Math: reduce header dependencies a bit.

src/Magnum/Animation/Test/InterpolationTest.cpp

@@ -33,6 +33,7 @@
 #include "Magnum/Math/CubicHermite.h"
 #include "Magnum/Math/DualQuaternion.h"
 #include "Magnum/Math/Half.h"
+#include "Magnum/Math/Packing.h"
 
 namespace Magnum { namespace Animation { namespace Test { namespace {
 

src/Magnum/Math/Half.h

@@ -29,10 +29,21 @@
  * @brief Class @ref Magnum::Math::Half, literal @link Magnum::Math::Literals::operator""_h() @endlink
  */
 
-#include "Magnum/Math/Packing.h"
+#include <utility>
+#include <Corrade/Utility/Utility.h>
+
+#include "Magnum/visibility.h"
+#include "Magnum/Math/Math.h"
+#include "Magnum/Math/Tags.h"
 
 namespace Magnum { namespace Math {
 
+#ifndef DOXYGEN_GENERATING_OUTPUT
+/* So we don't need to drag in the whole Packing.h */
+MAGNUM_EXPORT UnsignedShort packHalf(Float value);
+MAGNUM_EXPORT Float unpackHalf(UnsignedShort value);
+#endif
+
 /**
 @brief Half-precision float literal
 

src/Magnum/Math/Test/HalfTest.cpp

@@ -33,6 +33,7 @@
 #endif
 
 #include "Magnum/Math/Half.h"
+#include "Magnum/Math/Packing.h"
 #include "Magnum/Math/Vector3.h"
 #include "Magnum/Math/StrictWeakOrdering.h"