Seed with frame counter instead of SDL_GetTicks

Using SDL_GetTicks() to seed the Gravitron RNG caused many
reproducibility issues while syncing https://tasvideos.org/7575S . To
fix this, add a frame counter, which is a number that is incremented
every frame and never resets, and use it instead.

If someone needs to switch back to SDL_GetTicks() for old TASes, then
provide the -seed-use-sdl-getticks command-line option for them.

desktop_version/src/Script.cpp

@@ -3094,8 +3094,15 @@ void scriptclass::hardreset(void)
 {
     const bool version2_2 = GlitchrunnerMode_less_than_or_equal(Glitchrunner2_2);
 
-    /* The RNG is 32-bit. We don't _really_ need 64-bit... */
-    xoshiro_seed((Uint32) SDL_GetTicks64());
+    if (game.seed_use_sdl_getticks)
+    {
+        /* The RNG is 32-bit. We don't _really_ need 64-bit... */
+        xoshiro_seed((Uint32) SDL_GetTicks64());
+    }
+    else
+    {
+        xoshiro_seed(game.framecounter);
+    }
 
     //Game:
     game.hascontrol = true;