Implement isSrgb()

https://github.com/SFML/SFML/pull/1757

src/SFML/Graphics/RenderTexture.cpp

@@ -96,6 +96,14 @@ sfVector2u sfRenderTexture_getSize(const sfRenderTexture* renderTexture)
 }
 
 
+////////////////////////////////////////////////////////////
+sfBool sfRenderTexture_isSrgb(const sfRenderTexture* renderTexture)
+{
+    CSFML_CHECK_RETURN(renderTexture, sfFalse);
+    return renderTexture->This.isSrgb();
+}
+
+
 ////////////////////////////////////////////////////////////
 sfBool sfRenderTexture_setActive(sfRenderTexture* renderTexture, sfBool active)
 {

src/SFML/Graphics/RenderWindow.cpp

@@ -220,6 +220,14 @@ sfVector2u sfRenderWindow_getSize(const sfRenderWindow* renderWindow)
 }
 
 
+////////////////////////////////////////////////////////////
+sfBool sfRenderWindow_isSrgb(const sfRenderWindow* renderWindow)
+{
+    CSFML_CHECK_RETURN(renderWindow, sfFalse);
+    return renderWindow->This.isSrgb();
+}
+
+
 ////////////////////////////////////////////////////////////
 void sfRenderWindow_setSize(sfRenderWindow* renderWindow, sfVector2u size)
 {