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/torturethread.c

@@ -0,0 +1,128 @@
+/*
+  Copyright (C) 1997-2023 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
+  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.
+*/
+
+/* Simple test of the SDL threading code */
+
+#include <stdlib.h>
+#include <signal.h>
+
+#include <SDL3/SDL.h>
+#include <SDL3/SDL_main.h>
+#include <SDL3/SDL_test.h>
+
+#define NUMTHREADS 10
+
+static SDL_AtomicInt time_for_threads_to_die[NUMTHREADS];
+
+/* Call this instead of exit(), so we can clean up SDL: atexit() is evil. */
+static void
+quit(int rc)
+{
+    SDL_Quit();
+    /* Let 'main()' return normally */
+    if (rc != 0) {
+        exit(rc);
+    }
+}
+
+static int SDLCALL
+SubThreadFunc(void *data)
+{
+    while (!*(int volatile *)data) {
+        SDL_Delay(10);
+    }
+    return 0;
+}
+
+static int SDLCALL
+ThreadFunc(void *data)
+{
+    SDL_Thread *sub_threads[NUMTHREADS];
+    int flags[NUMTHREADS];
+    int i;
+    int tid = (int)(uintptr_t)data;
+
+    SDL_Log("Creating Thread %d\n", tid);
+
+    for (i = 0; i < NUMTHREADS; i++) {
+        char name[64];
+        (void)SDL_snprintf(name, sizeof(name), "Child%d_%d", tid, i);
+        flags[i] = 0;
+        sub_threads[i] = SDL_CreateThread(SubThreadFunc, name, &flags[i]);
+    }
+
+    SDL_Log("Thread '%d' waiting for signal\n", tid);
+    while (SDL_AtomicGet(&time_for_threads_to_die[tid]) != 1) {
+        ; /* do nothing */
+    }
+
+    SDL_Log("Thread '%d' sending signals to subthreads\n", tid);
+    for (i = 0; i < NUMTHREADS; i++) {
+        flags[i] = 1;
+        SDL_WaitThread(sub_threads[i], NULL);
+    }
+
+    SDL_Log("Thread '%d' exiting!\n", tid);
+
+    return 0;
+}
+
+int main(int argc, char *argv[])
+{
+    SDL_Thread *threads[NUMTHREADS];
+    int i;
+    SDLTest_CommonState *state;
+
+    /* Initialize test framework */
+    state = SDLTest_CommonCreateState(argv, 0);
+    if (state == NULL) {
+        return 1;
+    }
+
+    /* Enable standard application logging */
+    SDL_LogSetPriority(SDL_LOG_CATEGORY_APPLICATION, SDL_LOG_PRIORITY_INFO);
+
+    /* Load the SDL library */
+    if (SDL_Init(0) < 0) {
+        SDL_LogError(SDL_LOG_CATEGORY_APPLICATION, "Couldn't initialize SDL: %s\n", SDL_GetError());
+        return 1;
+    }
+
+    if (!SDLTest_CommonDefaultArgs(state, argc, argv)) {
+        SDLTest_CommonDestroyState(state);
+        return 1;
+    }
+
+    (void)signal(SIGSEGV, SIG_DFL);
+    for (i = 0; i < NUMTHREADS; i++) {
+        char name[64];
+        (void)SDL_snprintf(name, sizeof(name), "Parent%d", i);
+        SDL_AtomicSet(&time_for_threads_to_die[i], 0);
+        threads[i] = SDL_CreateThread(ThreadFunc, name, (void *)(uintptr_t)i);
+
+        if (threads[i] == NULL) {
+            SDL_LogError(SDL_LOG_CATEGORY_APPLICATION, "Couldn't create thread: %s\n", SDL_GetError());
+            quit(1);
+        }
+    }
+
+    for (i = 0; i < NUMTHREADS; i++) {
+        SDL_AtomicSet(&time_for_threads_to_die[i], 1);
+    }
+
+    for (i = 0; i < NUMTHREADS; i++) {
+        SDL_WaitThread(threads[i], NULL);
+    }
+    SDL_Quit();
+    SDLTest_CommonDestroyState(state);
+    return 0;
+}