Motivation for this change

Fixes

• Issue 17
  Cagebreak up to and including version 1.4.2 might have a use-after-free on destroying unmapped views. view->workspace was set on view creation. If the output containing this view was subsequently destroyed, the workspace was freed, leading to a use-after-free when the view was destroyed.
• Issue 18
  Cagebreak up to and including release 1.4.2 does not handle the position of xwayland views adequately.
• Issue 19
  Cagebreak up to and including release 1.4.2 does not handle unmanaged views adequately.
• Issue 20
  Cagebreak up to and including release 1.4.2 does not handle damaging adequately, when scanning out views.

Things done

• Tested using sandboxing (nix.useSandbox on NixOS, or option sandbox in nix.conf on non-NixOS linux)
• Built on platform(s)
  • NixOS
  • macOS
  • other Linux distributions
• Tested via one or more NixOS test(s) if existing and applicable for the change (look inside nixos/tests)
• Tested compilation of all pkgs that depend on this change using nix-shell -p nixpkgs-review --run "nixpkgs-review wip"
• Tested execution of all binary files (usually in ./result/bin/)
• Determined the impact on package closure size (by running nix path-info -S before and after)
• Ensured that relevant documentation is up to date
• Fits CONTRIBUTING.md.