Math: adapt to m.css Doxygen theme updates.

In particular, there's now warning about ignored documented friend
declarations. I don't have them documented, that's just Doxygen being
shitty.

src/Magnum/Math/Complex.h

@@ -89,8 +89,6 @@ See @ref transformations for brief introduction.
 @see @ref Magnum::Complex, @ref Magnum::Complexd, @ref Matrix3
 */
 template<class T> class Complex {
-    template<class> friend class Complex;
-
     public:
         typedef T Type; /**< @brief Underlying data type */
 
@@ -440,6 +438,11 @@ template<class T> class Complex {
         }
 
     private:
+        #ifndef DOXYGEN_GENERATING_OUTPUT
+        /* Doxygen copies the description from Magnum::Complex here. Ugh. */
+        template<class> friend class Complex;
+        #endif
+
         T _real, _imaginary;
 };
 

src/Magnum/Math/Quaternion.h

@@ -238,8 +238,6 @@ See @ref transformations for a brief introduction.
     @ref Matrix4
 */
 template<class T> class Quaternion {
-    template<class> friend class Quaternion;
-
     public:
         typedef T Type; /**< @brief Underlying data type */
 
@@ -588,6 +586,11 @@ template<class T> class Quaternion {
         Vector3<T> transformVectorNormalized(const Vector3<T>& vector) const;
 
     private:
+        #ifndef DOXYGEN_GENERATING_OUTPUT
+        /* Doxygen copies the description from Magnum::Quaternion here. Ugh. */
+        template<class> friend class Quaternion;
+        #endif
+
         /* Used to avoid including Functions.h */
         constexpr static T pow2(T value) {
             return value*value;