make sfRenderStates_default an extern const variable

include/CSFML/Graphics/RenderStates.h

@@ -50,4 +50,4 @@ typedef struct
 /// \brief Define the default values for a RenderState
 ///
 ////////////////////////////////////////////////////////////
-CSFML_GRAPHICS_API sfRenderStates sfRenderStates_default(void);
+CSFML_GRAPHICS_API const sfRenderStates sfRenderStates_default;

src/CSFML/Graphics/RenderStates.cpp

@@ -29,13 +29,9 @@
 
 
 ////////////////////////////////////////////////////////////
-sfRenderStates sfRenderStates_default()
+const sfRenderStates sfRenderStates_default = {
-{
-    sfRenderStates states = {
     sfBlendAlpha,
     sfTransform_Identity,
     nullptr,
     nullptr,
 };
-    return states;
-}