Inital context stuff and tests

Linking and  building is successfull and inital tests pass

tests/smoke_sdl3.c

@@ -0,0 +1,9 @@
+#include <SDL3/SDL.h>
+#include <stdio.h>
+
+int main(void)
+{
+    int v = SDL_GetVersion();
+    printf("SDL %d.%d.%d\n", SDL_VERSIONNUM_MAJOR(v), SDL_VERSIONNUM_MINOR(v), SDL_VERSIONNUM_MICRO(v));
+    return 0;
+}