lutok-0.5: minor bugfixes

Changes in version 0.5

Released on 2025/11/25.

• Use more modern autotools macros. Bump the minimum autoconf version to 2.68 to
  support this change.

• Modify build code to improve Lua 5.4 support.

• Replace std::auto_ptr use with std::unique_ptr use. This improves C++
  standard support and fixes the build with newer C++ standards.

Full Changelog: lutok-0.4...lutok-0.5