MSVC 2013 compatibility: workarounds for friend function declarations.

This is perfectly valid C++03 code, but MSVC can't cope with the <> in
it, so we need to make all templates friends, not only the
particular one. Sometimes it's internal compiler error, sometimes only
cryptic error message.

src/DebugTools/ShapeRenderer.h

@@ -138,7 +138,12 @@ new DebugTools::ShapeRenderer2D(shape, "red", debugDrawables);
 @todo Different drawing style for inverted shapes? (marking the "inside" somehow)
 */
 template<UnsignedInt dimensions> class MAGNUM_DEBUGTOOLS_EXPORT ShapeRenderer: public SceneGraph::Drawable<dimensions, Float> {
+    /* MSVC can't cope with <> here */
+    #ifndef CORRADE_MSVC2013_COMPATIBILITY
     friend void Implementation::createDebugMesh<>(ShapeRenderer<dimensions>&, const Shapes::Implementation::AbstractShape<dimensions>&);
+    #else
+    template<UnsignedInt dimensions_> friend void Implementation::createDebugMesh(ShapeRenderer<dimensions_>&, const Shapes::Implementation::AbstractShape<dimensions_>&);
+    #endif
 
     public:
         /**

src/Shapes/AbstractShape.h

@@ -50,7 +50,12 @@ brief introduction.
 @see AbstractShape2D, AbstractShape3D
 */
 template<UnsignedInt dimensions> class MAGNUM_SHAPES_EXPORT AbstractShape: public SceneGraph::AbstractGroupedFeature<dimensions, AbstractShape<dimensions>, Float> {
+    /* MSVC can't cope with <> here */
+    #ifndef CORRADE_MSVC2013_COMPATIBILITY
     friend const Implementation::AbstractShape<dimensions>& Implementation::getAbstractShape<>(const AbstractShape<dimensions>&);
+    #else
+    template<UnsignedInt dimensions_> friend const Implementation::AbstractShape<dimensions_>& Implementation::getAbstractShape(const Shapes::AbstractShape<dimensions_>&);
+    #endif
 
     public:
         enum: UnsignedInt {

src/Shapes/Composition.h

@@ -64,8 +64,14 @@ enum class CompositionOperation: UnsignedByte {
 Result of logical operations on shapes. See @ref shapes for brief introduction.
 */
 template<UnsignedInt dimensions> class MAGNUM_SHAPES_EXPORT Composition {
+    /* MSVC can't cope with <> here */
+    #ifndef CORRADE_MSVC2013_COMPATIBILITY
     friend Implementation::AbstractShape<dimensions>& Implementation::getAbstractShape<>(Composition<dimensions>&, std::size_t);
     friend const Implementation::AbstractShape<dimensions>& Implementation::getAbstractShape<>(const Composition<dimensions>&, std::size_t);
+    #else
+    template<UnsignedInt dimensions_> friend Implementation::AbstractShape<dimensions_>& Implementation::getAbstractShape(Composition<dimensions_>&, std::size_t);
+    template<UnsignedInt dimensions_> friend const Implementation::AbstractShape<dimensions_>& Implementation::getAbstractShape(const Composition<dimensions_>&, std::size_t);
+    #endif
     friend struct Implementation::ShapeHelper<Composition<dimensions>>;
 
     public: