configure: Revert sdl hunk of 4fa18c56. This breaks OSX

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

configure

@@ -2941,7 +2941,11 @@ if enabled libdc1394; then
     die "ERROR: No version of libdc1394 found "
 fi
 
-if check_pkg_config sdl SDL_version.h SDL_Linked_Version; then
+SDL_CONFIG="${cross_prefix}sdl-config"
+if "${SDL_CONFIG}" --version > /dev/null 2>&1; then
+    sdl_cflags=$("${SDL_CONFIG}" --cflags)
+    sdl_libs=$("${SDL_CONFIG}" --libs)
+    check_func_headers SDL.h SDL_Init $sdl_cflags $sdl_libs &&
     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