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_locale.h

@@ -1,6 +1,6 @@
 /*
   Simple DirectMedia Layer
-  Copyright (C) 1997-2020 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
@@ -47,44 +47,46 @@ typedef struct SDL_Locale
 } SDL_Locale;
 
 /**
- *  \brief Report the user's preferred locale.
+ * Report the user's preferred locale.
  *
- *  This returns an array of SDL_Locale structs, the final item zeroed out.
- *  When the caller is done with this array, it should call SDL_free() on
- *  the returned value; all the memory involved is allocated in a single
- *  block, so a single SDL_free() will suffice.
+ * This returns an array of SDL_Locale structs, the final item zeroed out.
+ * When the caller is done with this array, it should call SDL_free() on the
+ * returned value; all the memory involved is allocated in a single block, so
+ * a single SDL_free() will suffice.
  *
- *  Returned language strings are in the format xx, where 'xx' is an ISO-639
- *  language specifier (such as "en" for English, "de" for German, etc).
- *  Country strings are in the format YY, where "YY" is an ISO-3166 country
- *  code (such as "US" for the United States, "CA" for Canada, etc). Country
- *  might be NULL if there's no specific guidance on them (so you might get
- *  { "en", "US" } for American English, but { "en", NULL } means "English
- *  language, generically"). Language strings are never NULL, except to
- *  terminate the array.
+ * Returned language strings are in the format xx, where 'xx' is an ISO-639
+ * language specifier (such as "en" for English, "de" for German, etc).
+ * Country strings are in the format YY, where "YY" is an ISO-3166 country
+ * code (such as "US" for the United States, "CA" for Canada, etc). Country
+ * might be NULL if there's no specific guidance on them (so you might get {
+ * "en", "US" } for American English, but { "en", NULL } means "English
+ * language, generically"). Language strings are never NULL, except to
+ * terminate the array.
  *
- *  Please note that not all of these strings are 2 characters; some are
- *  three or more.
+ * Please note that not all of these strings are 2 characters; some are three
+ * or more.
  *
- *  The returned list of locales are in the order of the user's preference.
- *  For example, a German citizen that is fluent in US English and knows
- *  enough Japanese to navigate around Tokyo might have a list like:
- *  { "de", "en_US", "jp", NULL }. Someone from England might prefer British
- *  English (where "color" is spelled "colour", etc), but will settle for
- *  anything like it: { "en_GB", "en", NULL }.
+ * The returned list of locales are in the order of the user's preference. For
+ * example, a German citizen that is fluent in US English and knows enough
+ * Japanese to navigate around Tokyo might have a list like: { "de", "en_US",
+ * "jp", NULL }. Someone from England might prefer British English (where
+ * "color" is spelled "colour", etc), but will settle for anything like it: {
+ * "en_GB", "en", NULL }.
  *
- *  This function returns NULL on error, including when the platform does not
- *  supply this information at all.
+ * This function returns NULL on error, including when the platform does not
+ * supply this information at all.
  *
- *  This might be a "slow" call that has to query the operating system. It's
- *  best to ask for this once and save the results. However, this list can
- *  change, usually because the user has changed a system preference outside
- *  of your program; SDL will send an SDL_LOCALECHANGED event in this case,
- *  if possible, and you can call this function again to get an updated copy
- *  of preferred locales.
+ * This might be a "slow" call that has to query the operating system. It's
+ * best to ask for this once and save the results. However, this list can
+ * change, usually because the user has changed a system preference outside of
+ * your program; SDL will send an SDL_LOCALECHANGED event in this case, if
+ * possible, and you can call this function again to get an updated copy of
+ * preferred locales.
  *
- *   \return array of locales, terminated with a locale with a NULL language
- *           field. Will return NULL on error.
+ * \return array of locales, terminated with a locale with a NULL language
+ *         field. Will return NULL on error.
+ *
+ * \since This function is available since SDL 2.0.14.
  */
 extern DECLSPEC SDL_Locale * SDLCALL SDL_GetPreferredLocales(void);