Update to SDL 2.24.0 and add separate macOS UB2 dylib

Update mingw and macOS SDL libraries to 2.24.0. (MSVC .lib files and
Xcode project haven't been updated.)

There is now a separate SDL dylib for macOS Universal Binary 1 and 2
because SDL 2.24.0 dropped support for macOS 10.6 (which is last to
support x86). Documentation says SDL 2.24.0 also dropped macOS 10.7
and 10.8 too. So UB2 is now 10.9 or later while 10.5 to 10.8 live in
UB1.

Compiled using osxcross with macOS 11.3 SDK. Ran "strip -x" on Windows
and macOS libraries. Ad-hoc signed dylib using PyOxidizer rcodesign to
fix digest checksums after strip.

code/SDL2/include/SDL_test_common.h

@@ -1,6 +1,6 @@
 /*
   Simple DirectMedia Layer
-  Copyright (C) 1997-2021 Sam Lantinga <slouken@libsdl.org>
+  Copyright (C) 1997-2022 Sam Lantinga <slouken@libsdl.org>
 
   This software is provided 'as-is', without any express or implied
   warranty.  In no event will the authors be held liable for any damages
@@ -50,6 +50,7 @@
 #define VERBOSE_RENDER  0x00000004
 #define VERBOSE_EVENT   0x00000008
 #define VERBOSE_AUDIO   0x00000010
+#define VERBOSE_MOTION  0x00000020
 
 typedef struct
 {
@@ -114,6 +115,10 @@ typedef struct
     int gl_minor_version;
     int gl_debug;
     int gl_profile_mask;
+
+    /* Additional fields added in 2.0.18 */
+    SDL_Rect confine;
+
 } SDLTest_CommonState;
 
 #include "begin_code.h"
@@ -215,9 +220,10 @@ void SDLTest_CommonQuit(SDLTest_CommonState * state);
  *
  * \param renderer The renderer to draw to.
  * \param window The window whose information should be displayed.
+ * \param usedHeight Returns the height used, so the caller can draw more below.
  *
  */
-void SDLTest_CommonDrawWindowInfo(SDL_Renderer * renderer, SDL_Window * window);
+void SDLTest_CommonDrawWindowInfo(SDL_Renderer * renderer, SDL_Window * window, int * usedHeight);
 
 /* Ends C function definitions when using C++ */
 #ifdef __cplusplus