configure: check for SDL_Linked_Version instead of SDL_Init

This avoids the main/SDL_main declaration clash caused by SDL on
Windows and other platforms.

configure

@@ -2886,7 +2886,7 @@ if enabled libdc1394; then
     die "ERROR: No version of libdc1394 found "
 fi
 
-if check_pkg_config sdl SDL.h SDL_Init; then
+if check_pkg_config sdl SDL_version.h SDL_Linked_Version; then
     check_cpp_condition SDL.h "(SDL_MAJOR_VERSION<<16 | SDL_MINOR_VERSION<<8 | SDL_PATCHLEVEL) >= 0x010201" $sdl_cflags &&
     enable sdl &&
     check_struct SDL.h SDL_VideoInfo current_w $sdl_cflags && enable sdl_video_size