... actually update.

libs/SDL2/include/SDL_surface.h

@@ -118,6 +118,8 @@ typedef int (*SDL_blit) (struct SDL_Surface * src, SDL_Rect * srcrect,
 extern DECLSPEC SDL_Surface *SDLCALL SDL_CreateRGBSurface
     (Uint32 flags, int width, int height, int depth,
      Uint32 Rmask, Uint32 Gmask, Uint32 Bmask, Uint32 Amask);
+extern DECLSPEC SDL_Surface *SDLCALL SDL_CreateRGBSurfaceWithFormat
+    (Uint32 flags, int width, int height, int depth, Uint32 format);
 extern DECLSPEC SDL_Surface *SDLCALL SDL_CreateRGBSurfaceFrom(void *pixels,
                                                               int width,
                                                               int height,
@@ -127,6 +129,8 @@ extern DECLSPEC SDL_Surface *SDLCALL SDL_CreateRGBSurfaceFrom(void *pixels,
                                                               Uint32 Gmask,
                                                               Uint32 Bmask,
                                                               Uint32 Amask);
+extern DECLSPEC SDL_Surface *SDLCALL SDL_CreateRGBSurfaceWithFormatFrom
+    (void *pixels, int width, int height, int depth, int pitch, Uint32 format);
 extern DECLSPEC void SDLCALL SDL_FreeSurface(SDL_Surface * surface);
 
 /**
@@ -184,6 +188,12 @@ extern DECLSPEC SDL_Surface *SDLCALL SDL_LoadBMP_RW(SDL_RWops * src,
 /**
  *  Save a surface to a seekable SDL data stream (memory or file).
  *
+ *  Surfaces with a 24-bit, 32-bit and paletted 8-bit format get saved in the
+ *  BMP directly. Other RGB formats with 8-bit or higher get converted to a
+ *  24-bit surface or, if they have an alpha mask or a colorkey, to a 32-bit
+ *  surface before they are saved. YUV and paletted 1-bit and 4-bit formats are
+ *  not supported.
+ *
  *  If \c freedst is non-zero, the stream will be closed after being written.
  *
  *  \return 0 if successful or -1 if there was an error.