2.35.1 bugfix release

* Fix prefix update from persistent files.
* Fix creation of the library compatibility link.
* Fix identification of the application using a given icon.
* Fix support for context-specific applications lists when generating launchers.
* Ensure correct permissions on icons, despite ImageMagick messing them up.
* Rework game script identification by hash to rely on --list-archives,
  fixing the identification of some archives with multiple valid MD5 hashes.
* Gentoo: Fix output path for generated packages.
* Gentoo: Update packages installation instructions.
* Gentoo: Show a message for each package being built.
* Gentoo: Fix generation of packages compressed with xz.
* Gentoo: Generate packages in a "games-playit" sub-directory.
* Unity3D: Do not try to apply Linux workarounds to Windows games.
* Unity3D: Prevent inclusion of binaries/libraries for a wrong architecture.
* WINE: Improve support for custom path to wine command.
* WINE: Print an explicit error when trying to write a launcher for a package with no architecture set.