Document what the remaining <Corrade/Utility/TypeTraits.h> are for.

src/Magnum/Math/Dual.h

@@ -33,7 +33,7 @@
 #include <Corrade/Utility/Debug.h>
 #endif
 #include <Corrade/Utility/StlMath.h>
-#include <Corrade/Utility/TypeTraits.h>
+#include <Corrade/Utility/TypeTraits.h> /* CORRADE_HAS_TYPE() */
 
 #include "Magnum/Math/Angle.h"
 #include "Magnum/Math/Tags.h"

src/Magnum/Vk/Implementation/structureHelpers.h

@@ -27,7 +27,7 @@
 
 #include <Corrade/Containers/Reference.h>
 #include <Corrade/Utility/Assert.h>
-#include <Corrade/Utility/TypeTraits.h>
+#include <Corrade/Utility/TypeTraits.h> /* CORRADE_HAS_TYPE() */
 
 #include "Magnum/Magnum.h"
 #include "Magnum/Vk/Vulkan.h"

src/Magnum/Vk/TypeTraits.h

@@ -30,7 +30,7 @@
  * @m_since_latest
  */
 
-#include <Corrade/Utility/TypeTraits.h>
+#include <Corrade/Utility/TypeTraits.h> /* CORRADE_HAS_TYPE() */
 
 namespace Magnum { namespace Vk {