video: Fix compiler warning about SDL_ReadSurfacePixel not being declared.

(this was legal before, but the Android NDK wants to make sure we didn't mean
for this function to be marked `static` since it didn't have a formal
declaration before its definition and might only be used in the one source
file.)

src/video/SDL_surface.c

@@ -21,6 +21,7 @@
 #include "SDL_internal.h"
 
 #include "SDL_sysvideo.h"
+#include "SDL_video_c.h"
 #include "SDL_blit.h"
 #include "SDL_RLEaccel_c.h"
 #include "SDL_surface_pixel_impl.h"
@@ -35,8 +36,7 @@ SDL_COMPILE_TIME_ASSERT(surface_size_assumptions,
 
 SDL_COMPILE_TIME_ASSERT(can_indicate_overflow, SDL_SIZE_MAX > SDL_MAX_SINT32);
 
-int
-SDL_ReadSurfacePixel(SDL_Surface *surface, int x, int y, Uint8 *r, Uint8 *g, Uint8 *b, Uint8 *a)
+int SDL_ReadSurfacePixel(SDL_Surface *surface, int x, int y, Uint8 *r, Uint8 *g, Uint8 *b, Uint8 *a)
 {
     return SDL_ReadSurfacePixel_impl(surface, x, y, r, g, b, a);
 }