Ultrono Arena macOS client

Two macOS distributions are produced:

- The folder distribution has uacl, autoexec.cfg, and assets side by side.
  Run ./uacl from Terminal or double-click uacl. Edit autoexec.cfg directly in
  that folder.
- The app distribution has Ultrono Arena.app for normal double-click use.
  Its first launch creates an editable config at:

  ~/Library/Application Support/Ultrono Arena/autoexec.cfg

The app bundle contains the default config and game assets. Menu-based config
saves write to the Application Support copy.

Basic controls:
- Esc opens and closes the menu.
- Tilde/backtick opens and closes the console.
- Up arrow switches to fullscreen.
- Down arrow switches back to windowed mode.
- F3 marks you ready; F4 marks you not ready.

Default movement keys are R/F/D/G plus Space to jump. Mouse buttons fire the
default weapon binds from autoexec.cfg.

To join a server, use the menu server browser or open the console and run:

  connect HOST:PORT

For a local server on the default port:

  connect localhost

You can customize controls and settings in autoexec.cfg.
