message: Export more lib-common symbols
diff: #include <visionaray/math/forward.h>
  #include <visionaray/math/vector.h>
  +#include "../export.h"
  +
  namespace visionaray
  {
  namespace sg
  @@ -20,7 +22,7 @@ namespace sg
  // Material base class
  //
  -class material
  +class VSNRAY_COMMON_EXPORT material
  {
  public:
  virtual ~material() {}
  @@ -38,7 +40,7 @@ private:
  // Wavefront obj material
  //
  -struct obj_material : material
  +struct VSNRAY_COMMON_EXPORT obj_material : material
  {
  // Ambient color
  vec3 ca = { 0.2f, 0.2f, 0.2f };
  @@ -76,7 +78,7 @@ struct obj_material : material
  // Glass material
  //
  -struct glass_material : material
  +struct VSNRAY_COMMON_EXPORT glass_material : material
  {
  // Transmissive color
  vec3 ct = { 0.8f, 0.8f, 0.8f };
  @@ -93,7 +95,7 @@ struct glass_material : material
  // Metal material
  //
  -struct metal_material : material
  +struct VSNRAY_COMMON_EXPORT metal_material : material
  {
  // Roughness
  float roughness = 0.0f;
  @@ -110,7 +112,7 @@ struct metal_material : material
  // Disney principled material
  //
  -struct disney_material : material
  +struct VSNRAY_COMMON_EXPORT disney_material : material
  {
  // Base color
  vec4 base_color = vec4(0.0f);
  