winrt: Removed WinRT/Windows Phone/UWP support.

Fixes #10724.

docs/README-migration.md

@@ -836,6 +836,9 @@ The following hints have been removed:
 * SDL_HINT_WINDOWS_DISABLE_THREAD_NAMING - SDL now properly handles the 0x406D1388 Exception if no debugger intercepts it, preventing its propagation.
 * SDL_HINT_WINDOWS_FORCE_MUTEX_CRITICAL_SECTIONS - Slim Reader/Writer Locks are always used if available
 * SDL_HINT_WINDOWS_NO_CLOSE_ON_ALT_F4 - replaced with SDL_HINT_WINDOWS_CLOSE_ON_ALT_F4, defaulting to SDL_TRUE
+* SDL_HINT_WINRT_HANDLE_BACK_BUTTON - WinRT support was removed in SDL3.
+* SDL_HINT_WINRT_PRIVACY_POLICY_LABEL - WinRT support was removed in SDL3.
+* SDL_HINT_WINRT_PRIVACY_POLICY_URL - WinRT support was removed in SDL3.
 * SDL_HINT_XINPUT_USE_OLD_JOYSTICK_MAPPING
 * SDL_HINT_AUDIO_DEVICE_APP_NAME - replaced by either using the appname param to SDL_SetAppMetadata() or setting SDL_PROP_APP_METADATA_NAME_STRING with SDL_SetAppMetadataProperty()
 
@@ -1118,11 +1121,14 @@ Using it is really simple: Just `#include <SDL3/SDL_main.h>` in the source file
 Several platform-specific entry point functions have been removed as unnecessary. If for some reason you explicitly need them, here are easy replacements:
 
 ```c
-#define SDL_WinRTRunApp(MAIN_FUNC, RESERVED)  SDL_RunApp(0, NULL, MAIN_FUNC, RESERVED)
 #define SDL_UIKitRunApp(ARGC, ARGV, MAIN_FUNC)  SDL_RunApp(ARGC, ARGV, MAIN_FUNC, NULL)
 #define SDL_GDKRunApp(MAIN_FUNC, RESERVED)  SDL_RunApp(0, NULL, MAIN_FUNC, RESERVED)
 ```
 
+The following functions have been removed:
+* SDL_WinRTRunApp() - WinRT support was removed in SDL3.
+
+
 ## SDL_messagebox.h
 
 The buttonid field of SDL_MessageBoxButtonData has been renamed buttonID.
@@ -1275,7 +1281,6 @@ The following platform preprocessor macros have been renamed:
 | `__VITA__`        | `SDL_PLATFORM_VITA`       |
 | `__WIN32__`       | `SDL_PLATFORM_WIN32`      |
 | `__WINGDK__`      | `SDL_PLATFORM_WINGDK`     |
-| `__WINRT__`       | `SDL_PLATFORM_WINRT`      |
 | `__XBOXONE__`     | `SDL_PLATFORM_XBOXONE`    |
 | `__XBOXSERIES__`  | `SDL_PLATFORM_XBOXSERIES` |
 
@@ -1288,6 +1293,8 @@ The following platform preprocessor macros have been removed:
 * `__NACL__`
 * `__PNACL__`
 * `__WINDOWS__`
+* `__WINRT__`
+
 
 ## SDL_quit.h
 
@@ -1850,10 +1857,12 @@ SDL_RequestAndroidPermission is no longer a blocking call; the caller now provid
 SDL_iPhoneSetAnimationCallback() and SDL_iPhoneSetEventPump() have been renamed to SDL_SetiOSAnimationCallback() and SDL_SetiOSEventPump(), respectively. SDL2 has had macros to provide this new name with the old symbol since the introduction of the iPad, but now the correctly-named symbol is the only option.
 
 The following functions have been removed:
+* SDL_GetWinRTFSPathUNICODE() - WinRT support was removed in SDL3.
+* SDL_GetWinRTFSPathUTF8() - WinRT support was removed in SDL3.
 * SDL_RenderGetD3D11Device() - replaced with the "SDL.renderer.d3d11.device" property
 * SDL_RenderGetD3D12Device() - replaced with the "SDL.renderer.d3d12.device" property
 * SDL_RenderGetD3D9Device() - replaced with the "SDL.renderer.d3d9.device" property
-* SDL_GetWinRTFSPathUNICODE() - Use SDL_GetWinRTFSPath() and SDL_iconv_string to convert from UTF-8 to UTF-16.
+* SDL_WinRTGetDeviceFamily() - WinRT support was removed in SDL3.
 
 The following functions have been renamed:
 * SDL_AndroidBackButton() => SDL_SendAndroidBackButton()
@@ -1874,8 +1883,6 @@ The following functions have been renamed:
 * SDL_LinuxSetThreadPriorityAndPolicy() => SDL_SetLinuxThreadPriorityAndPolicy(), returns SDL_bool
 * SDL_OnApplicationDidBecomeActive() => SDL_OnApplicationDidEnterForeground()
 * SDL_OnApplicationWillResignActive() => SDL_OnApplicationWillEnterBackground()
-* SDL_WinRTGetDeviceFamily() => SDL_GetWinRTDeviceFamily()
-* SDL_GetWinRTFSPathUTF8() => SDL_GetWinRTFSPath()
 * SDL_iOSSetAnimationCallback() => SDL_SetiOSAnimationCallback(), returns SDL_bool
 * SDL_iOSSetEventPump() => SDL_SetiOSEventPump()
 * SDL_iPhoneSetAnimationCallback() => SDL_SetiOSAnimationCallback(), returns SDL_bool