Update SDL to 2.0.22.

On Android, `SDL_RWops` no longer stores a plain file descriptor,
so the `AAsset` API must be used instead:
https://developer.android.com/ndk/reference/group/asset

`HAVE_INOTIFY` is required on Linux at the moment, but the bug will be
fixed in the next SDL release.

project/lib/overrides/sdl/include/SDL_config_linux.h

@@ -53,6 +53,8 @@
 #define HAVE_LIBC 1
 #if HAVE_LIBC
 
+#define HAVE_INOTIFY 1
+
 /* Useful headers */
 #define HAVE_ALLOCA_H 1
 #define HAVE_SYS_TYPES_H 1