Windows build fixes.

src/AbstractTexture.h

@@ -555,7 +555,7 @@ You can also use the constructor directly instead of binary OR:
 InternalFormat fmt2(Components::RGBA, ComponentType::NormalizedUnsignedByte);
 @endcode
 */
-class AbstractTexture::InternalFormat {
+class MAGNUM_EXPORT AbstractTexture::InternalFormat {
     public:
         /** @brief Constructor from component count and data type per component */
         InternalFormat(Components components, ComponentType type);
@@ -599,7 +599,7 @@ template<> struct AbstractTexture::DataHelper<1> {
         glTexSubImage1D(target, mipLevel, offset[0], image->dimensions()[0], static_cast<GLenum>(image->components()), static_cast<GLenum>(image->type()), image->data());
     }
 };
-template<> struct AbstractTexture::DataHelper<2> {
+template<> struct MAGNUM_EXPORT AbstractTexture::DataHelper<2> {
     enum class Target: GLenum {
         Texture2D = GL_TEXTURE_2D,
         Texture1DArray = GL_TEXTURE_1D_ARRAY,
@@ -622,7 +622,7 @@ template<> struct AbstractTexture::DataHelper<2> {
         glTexSubImage2D(target, mipLevel, offset[0], offset[1], image->dimensions()[0], 1, static_cast<GLenum>(image->components()), static_cast<GLenum>(image->type()), image->data());
     }
 };
-template<> struct AbstractTexture::DataHelper<3> {
+template<> struct MAGNUM_EXPORT AbstractTexture::DataHelper<3> {
     enum class Target: GLenum {
         Texture3D = GL_TEXTURE_3D,
         Texture2DArray = GL_TEXTURE_2D_ARRAY

src/Light.h

@@ -28,7 +28,7 @@ namespace Magnum {
  *
  * Provides cached light position.
  */
-class Light: public Object {
+class MAGNUM_EXPORT Light: public Object {
     public:
         /**
          * @brief Constructor

src/MeshTools/FlipNormals.h

@@ -29,7 +29,7 @@ namespace Magnum { namespace MeshTools {
 The same as flipNormals(std::vector<unsigned int>&, std::vector<Vector3>&),
 but flips only face winding.
 */
-void flipFaceWinding(std::vector<unsigned int>& indices);
+void MESHTOOLS_EXPORT flipFaceWinding(std::vector<unsigned int>& indices);
 
 /**
 @brief Flip mesh normals
@@ -37,7 +37,7 @@ void flipFaceWinding(std::vector<unsigned int>& indices);
 The same as flipNormals(std::vector<unsigned int>&, std::vector<Vector3>&),
 but flips only normals, not face winding.
 */
-void flipNormals(std::vector<Vector3>& normals);
+void MESHTOOLS_EXPORT flipNormals(std::vector<Vector3>& normals);
 
 /**
 @brief Flip mesh normals and face winding