VIDEO: Initialize SDL_version structures that might not be completely set

B. Scott Michel's run of clang memory sanitizer identified that  some
fields in these structures in some versions on some platforms.

sim_video.c

@@ -2252,7 +2252,7 @@ return 0;
 const char *vid_version(void)
 {
 static char SDLVersion[160];
-SDL_version compiled, running;
+SDL_version compiled = { 0}, running = { 0};
 
 SDL_GetVersion(&running);