x265: 3.2 -> 3.4

[titouanco]

• Change version from 3.2 to 3.4
• Use fetchFromBitbucket to fetch the archive from multicoreware/x265_git instead of the videolan server (doesn't have the latest version)
• Remove the ARM patch, doesn't work anymore but doesn't seems necessary since this commit

Motivation for this change

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.