Fix frame update logic and emulator support

- Fix basic1.cpp loop to handle set_frame_updates(true) correctly with sleep
- Update emulator loop for concurrent input and frame updates
- Update emulator for SFML 3.0 compatibility
- Add INPUT.FRAME_TICK constant to Lua bindings
- Enable frame updates in snake.lua example

games/lua_bindings.cpp

@@ -236,6 +236,10 @@ static void register_input_constants(lua_State* L) {
     lua_pushstring(L, "GESTURE");
     lua_pushinteger(L, 6);
     lua_settable(L, -3);
+
+    lua_pushstring(L, "FRAME_TICK");
+    lua_pushinteger(L, 7);
+    lua_settable(L, -3);
     
     lua_setglobal(L, "INPUT");
 }