Vendor raptor source files (was embedded gitlink)

Tree vendored at upstream 0019c5dd; origin + license recorded in
raptor/VENDOR.txt. Windows SDL dev packages excluded via .gitignore.

raptor/include/SDL2-devel-2.28.2-VC/SDL2-2.28.2/docs/README-n3ds.md

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+# Nintendo 3DS
+
+SDL port for the Nintendo 3DS [Homebrew toolchain](https://devkitpro.org/) contributed by:
+
+-   [Pierre Wendling](https://github.com/FtZPetruska)
+
+Credits to:
+
+-   The awesome people who ported SDL to other homebrew platforms.
+-   The Devkitpro team for making all the tools necessary to achieve this.
+
+## Building
+
+To build for the Nintendo 3DS, make sure you have devkitARM and cmake installed and run:
+
+```bash
+cmake -S. -Bbuild -DCMAKE_TOOLCHAIN_FILE="$DEVKITPRO/cmake/3DS.cmake" -DCMAKE_BUILD_TYPE=Release
+cmake --build build
+cmake --install build
+```
+
+## Notes
+
+-   Currently only software rendering is supported.
+-   SDL2main should be used to ensure ROMFS is enabled.
+-   By default, the extra L2 cache and higher clock speeds of the New 2/3DS lineup are enabled. If you wish to turn it off, use `osSetSpeedupEnable(false)` in your main function.
+-   `SDL_GetBasePath` returns the romfs root instead of the executable's directory.
+-   The Nintendo 3DS uses a cooperative threading model on a single core, meaning a thread will never yield unless done manually through the `SDL_Delay` functions, or blocking waits (`SDL_LockMutex`, `SDL_SemWait`, `SDL_CondWait`, `SDL_WaitThread`). To avoid starving other threads, `SDL_SemTryWait` and `SDL_SemWaitTimeout` will yield if they fail to acquire the semaphore, see https://github.com/libsdl-org/SDL/pull/6776 for more information.