2.33.1 bugfix release

* Prevent default values for LD_PRELOAD_SOURCE from overriding maintainer-set ones.
* Add support for completion with some interactive shells:
  - fish
  - zsh
* DOSBox games: Fix detection of MS-DOS binaries through file/libmagic.
* UNity3D games: Improve error message when no binary is found.
* WINE games: Fix inclusion of the winetricks wrapper when using a non-default Direct3D renderer.
* WINE games: Prevent the creation of an empty registry-scripts directory.