Math: fix a copypaste error with Frustumd debug output extern template.

doc/changelog.dox

@@ -559,6 +559,9 @@ See also:
 -   Fixed an assertion when using @ref MeshTools::removeDuplicates() on an
     interleaved @ref Trade::MeshData that included padding at the beginning or
     end of each vertex
+-   Fixed a silly mistake where there was no @cpp extern template @ce for a
+    @ref Frustumd debug printer but two declarations for the float version
+    instead (see [mosra/magnum#545](https://github.com/mosra/magnum/issues/545))
 -   Fixed @ref MeshTools::compile() to properly take into account index buffer
     offsets
 -   Fixed @ref MeshTools::removeDuplicates() to not take into account random

doc/credits.dox

@@ -120,6 +120,8 @@ Are the below lists missing your name or something's wrong?
     @ref ResourceManager, warning fixes
 -   **Denis Igorevich Lobanov** ([\@denislobanov](https://github.com/denislobanov))
     --- math fixes
+-   **[\@DJQuardaboff](https://github.com/DJQuardaboff)** --- discovery of a
+    silly mistake with @ref Frustumd debug output printer
 -   **[\@dlardi](https://github.com/dlardi)** --- WGL-related bugfixes
 -   **Eliot Saba** ([\@staticfloat](https://github.com/staticfloat)) ---
     macOS-related updates to @ref Platform::GlfwApplication

src/Magnum/Math/Frustum.h

@@ -267,7 +267,7 @@ template<class T> Corrade::Utility::Debug& operator<<(Corrade::Utility::Debug& d
 /* Explicit instantiation for commonly used types */
 #ifndef DOXYGEN_GENERATING_OUTPUT
 extern template MAGNUM_EXPORT Corrade::Utility::Debug& operator<<(Corrade::Utility::Debug&, const Frustum<Float>&);
-extern template MAGNUM_EXPORT Corrade::Utility::Debug& operator<<(Corrade::Utility::Debug&, const Frustum<Float>&);
+extern template MAGNUM_EXPORT Corrade::Utility::Debug& operator<<(Corrade::Utility::Debug&, const Frustum<Double>&);
 #endif
 #endif