feat(gx): add incomplete 'CGxDeviceGLSDL' (#2)

* chore(build): add vendored SDL 3.0.0 library

* chore(build): add vendored glew-cmake-2.2.0 library

* feat(console): in the presence of -opengl launch flag, change GxApi to OpenGl

* feat(gx): add uncompleted CGxDeviceGLSDL targeting Windows and Linux

* chore(build): change SDL3 linkage from shared (bad) to to static (good)

vendor/sdl-3.0.0/docs/README.md

@@ -0,0 +1,57 @@
+# Simple DirectMedia Layer
+
+https://www.libsdl.org/
+
+Simple DirectMedia Layer is a cross-platform development library designed
+to provide low level access to audio, keyboard, mouse, joystick, and graphics
+hardware via OpenGL and Direct3D. It is used by video playback software,
+emulators, and popular games including Valve's award winning catalog
+and many Humble Bundle games.
+
+SDL officially supports Windows, macOS, Linux, iOS, and Android.
+Support for other platforms may be found in the source code.
+
+SDL is written in C, works natively with C++, and there are bindings 
+available for several other languages, including C# and Python.
+
+This library is distributed under the zlib license, which can be found
+in the file "LICENSE.txt".
+
+The best way to learn how to use SDL is to check out the header files in
+the "include" subdirectory and the programs in the "test" subdirectory.
+The header files and test programs are well commented and always up to date.
+
+More documentation and FAQs are available online at [the wiki](http://wiki.libsdl.org/)
+
+- [Android](README-android.md)
+- [CMake](README-cmake.md)
+- [DynAPI](README-dynapi.md)
+- [Emscripten](README-emscripten.md)
+- [GDK](README-gdk.md)
+- [Git](README-git.md)
+- [iOS](README-ios.md)
+- [Linux](README-linux.md)
+- [macOS](README-macos.md)
+- [Supported Platforms](README-platforms.md)
+- [Porting information](README-porting.md)
+- [PSP](README-psp.md)
+- [PS2](README-ps2.md)
+- [Raspberry Pi](README-raspberrypi.md)
+- [Touch](README-touch.md)
+- [Versions](README-versions.md)
+- [Windows](README-windows.md)
+- [WinRT](README-winrt.md)
+- [PSVita](README-vita.md)
+- [Nokia N-Gage](README-ngage.md)
+
+If you need help with the library, or just want to discuss SDL related
+issues, you can join the [SDL Discourse](https://discourse.libsdl.org/),
+which can be used as a web forum or a mailing list, at your preference.
+
+If you want to report bugs or contribute patches, please submit them to
+[our bug tracker](https://github.com/libsdl-org/SDL/issues)
+
+Enjoy!
+
+
+Sam Lantinga <mailto:slouken@libsdl.org>