Update SDL to the latest source code (2.0.9 + e1e13e154128)

libs/SDL2/include/SDL_surface.h

@@ -248,6 +248,13 @@ extern DECLSPEC int SDLCALL SDL_SetSurfaceRLE(SDL_Surface * surface,
 extern DECLSPEC int SDLCALL SDL_SetColorKey(SDL_Surface * surface,
                                             int flag, Uint32 key);
 
+/**
+ *  \brief Returns whether the surface has a color key
+ *
+ *  \return SDL_TRUE if the surface has a color key, or SDL_FALSE if the surface is NULL or has no color key
+ */
+extern DECLSPEC SDL_bool SDLCALL SDL_HasColorKey(SDL_Surface * surface);
+
 /**
  *  \brief Gets the color key (transparent pixel) in a blittable surface.
  *