Shapes: properly export all instances.

Not sure why this wasn't done already.

src/Magnum/Shapes/Box.cpp

@@ -31,7 +31,9 @@ template<UnsignedInt dimensions> Box<dimensions> Box<dimensions>::transformed(co
     return Box<dimensions>(matrix*_transformation);
 }
 
-template class Box<2>;
-template class Box<3>;
+#ifndef DOXYGEN_GENERATING_OUTPUT
+template class MAGNUM_SHAPES_EXPORT Box<2>;
+template class MAGNUM_SHAPES_EXPORT Box<3>;
+#endif
 
 }}

src/Magnum/Shapes/Line.cpp

@@ -36,7 +36,9 @@ template<UnsignedInt dimensions> Line<dimensions> Line<dimensions>::transformed(
 }
 
 /* Explicitly instantiate the templates */
-template class Line<2>;
-template class Line<3>;
+#ifndef DOXYGEN_GENERATING_OUTPUT
+template class MAGNUM_SHAPES_EXPORT Line<2>;
+template class MAGNUM_SHAPES_EXPORT Line<3>;
+#endif
 
 }}

src/Magnum/Shapes/Point.cpp

@@ -34,7 +34,9 @@ template<UnsignedInt dimensions> Point<dimensions> Point<dimensions>::transforme
     return Point<dimensions>(matrix.transformPoint(_position));
 }
 
-template class Point<2>;
-template class Point<3>;
+#ifndef DOXYGEN_GENERATING_OUTPUT
+template class MAGNUM_SHAPES_EXPORT Point<2>;
+template class MAGNUM_SHAPES_EXPORT Point<3>;
+#endif
 
 }}