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/test/testutils.h

@@ -0,0 +1,24 @@
+/*
+  Copyright (C) 1997-2023 Sam Lantinga <slouken@libsdl.org>
+  Copyright 2022 Collabora Ltd.
+
+  This software is provided 'as-is', without any express or implied
+  warranty.  In no event will the authors be held liable for any damages
+  arising from the use of this software.
+
+  Permission is granted to anyone to use this software for any purpose,
+  including commercial applications, and to alter it and redistribute it
+  freely.
+*/
+
+#ifndef TESTUTILS_H
+#define TESTUTILS_H
+
+#include <SDL3/SDL.h>
+
+SDL_Texture *LoadTexture(SDL_Renderer *renderer, const char *file, SDL_bool transparent,
+                         int *width_out, int *height_out);
+char *GetNearbyFilename(const char *file);
+char *GetResourceFilename(const char *user_specified, const char *def);
+
+#endif