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_version.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
@@ -58,8 +58,8 @@ typedef struct SDL_version
 /* Printable format: "%d.%d.%d", MAJOR, MINOR, PATCHLEVEL
 */
 #define SDL_MAJOR_VERSION   2
-#define SDL_MINOR_VERSION   0
-#define SDL_PATCHLEVEL      16
+#define SDL_MINOR_VERSION   24
+#define SDL_PATCHLEVEL      0
 
 /**
  * Macro to determine SDL version program was compiled against.
@@ -83,6 +83,8 @@ typedef struct SDL_version
     (x)->patch = SDL_PATCHLEVEL;                    \
 }
 
+/* TODO: Remove this whole block in SDL 3 */
+#if SDL_MAJOR_VERSION < 3
 /**
  *  This macro turns the version numbers into a numeric value:
  *  \verbatim
@@ -90,21 +92,35 @@ typedef struct SDL_version
     \endverbatim
  *
  *  This assumes that there will never be more than 100 patchlevels.
+ *
+ *  In versions higher than 2.9.0, the minor version overflows into
+ *  the thousands digit: for example, 2.23.0 is encoded as 4300,
+ *  and 2.255.99 would be encoded as 25799.
+ *  This macro will not be available in SDL 3.x.
  */
 #define SDL_VERSIONNUM(X, Y, Z)                     \
     ((X)*1000 + (Y)*100 + (Z))
 
 /**
  *  This is the version number macro for the current SDL version.
+ *
+ *  In versions higher than 2.9.0, the minor version overflows into
+ *  the thousands digit: for example, 2.23.0 is encoded as 4300.
+ *  This macro will not be available in SDL 3.x.
+ *
+ *  Deprecated, use SDL_VERSION_ATLEAST or SDL_VERSION instead.
  */
 #define SDL_COMPILEDVERSION \
     SDL_VERSIONNUM(SDL_MAJOR_VERSION, SDL_MINOR_VERSION, SDL_PATCHLEVEL)
+#endif /* SDL_MAJOR_VERSION < 3 */
 
 /**
  *  This macro will evaluate to true if compiled with SDL at least X.Y.Z.
  */
 #define SDL_VERSION_ATLEAST(X, Y, Z) \
-    (SDL_COMPILEDVERSION >= SDL_VERSIONNUM(X, Y, Z))
+    ((SDL_MAJOR_VERSION >= X) && \
+     (SDL_MAJOR_VERSION > X || SDL_MINOR_VERSION >= Y) && \
+     (SDL_MAJOR_VERSION > X || SDL_MINOR_VERSION > Y || SDL_PATCHLEVEL >= Z))
 
 /**
  * Get the version of SDL that is linked against your program.
@@ -118,6 +134,8 @@ typedef struct SDL_version
  *
  * \param ver the SDL_version structure that contains the version information
  *
+ * \since This function is available since SDL 2.0.0.
+ *
  * \sa SDL_GetRevision
  */
 extern DECLSPEC void SDLCALL SDL_GetVersion(SDL_version * ver);
@@ -145,6 +163,8 @@ extern DECLSPEC void SDLCALL SDL_GetVersion(SDL_version * ver);
  * \returns an arbitrary string, uniquely identifying the exact revision of
  *          the SDL library in use.
  *
+ * \since This function is available since SDL 2.0.0.
+ *
  * \sa SDL_GetVersion
  */
 extern DECLSPEC const char *SDLCALL SDL_GetRevision(void);
@@ -153,10 +173,22 @@ extern DECLSPEC const char *SDLCALL SDL_GetRevision(void);
  * Obsolete function, do not use.
  *
  * When SDL was hosted in a Mercurial repository, and was built carefully,
- * this would return the revision number that the build was created from.
- * This number was not reliable for several reasons, but more importantly,
- * SDL is now hosted in a git repository, which does not offer numbers at
- * all, only hashes. This function only ever returns zero now. Don't use it.
+ * this would return the revision number that the build was created from. This
+ * number was not reliable for several reasons, but more importantly, SDL is
+ * now hosted in a git repository, which does not offer numbers at all, only
+ * hashes. This function only ever returns zero now. Don't use it.
+ *
+ * Before SDL 2.0.16, this might have returned an unreliable, but non-zero
+ * number.
+ *
+ * \deprecated Use SDL_GetRevision() instead; if SDL was carefully built, it
+ *             will return a git hash.
+ *
+ * \returns zero, always, in modern SDL releases.
+ *
+ * \since This function is available since SDL 2.0.0.
+ *
+ * \sa SDL_GetRevision
  */
 extern SDL_DEPRECATED DECLSPEC int SDLCALL SDL_GetRevisionNumber(void);