Motivation for this change

• Critical security fixes
• Two new 'compact' themes available in Firefox, dark and light, based on the Firefox Developer Edition theme
• Lightweight themes are now applied in private browsing windows
• Reader Mode now displays estimated reading time for the page
• Updated the design of site permission requests to make them harder to miss and easier to understand
• New visual design for audio and video controls
• Ended Firefox Linux support for processors older than Pentium 4 and AMD Opteron
• Support for WebM video with alpha, which allows playing videos with transparent backgrounds

https://www.mozilla.org/en-US/firefox/53.0/releasenotes/
https://www.mozilla.org/en-US/firefox/52.1.0/releasenotes/
https://www.mozilla.org/en-US/security/advisories/mfsa2017-10/

Tested (playing a YouTube video) both firefox-bin and firefox-esr. firefox-esr may not work with old profiles made with older firefox-bin, but it works with a fresh profile.

I could not build firefox (source package) yet. It now requires Rust and Cargo, but adding cargo and rustc (or rust) to nativeBuildInputs does not work.
[edit] I edited a wrong file. Now configure succeeds and compiling. [/edit]
[edit] I got /tmp/nix-build-firefox-unwrapped-53.0.drv-0/firefox-53.0/extensions/spellcheck/hunspell/glue/mozHunspell.cpp:203:34: error: 'class Hunspell' has no member named 'get_dict_encoding'. Maybe hunspell need to be updated. [/edit]

Things done

• Tested using sandboxing
  (nix.useSandbox on NixOS,
  or option build-use-sandbox in nix.conf
  on non-NixOS)
• Built on platform(s)
  • NixOS
  • macOS
  • Linux
• Tested compilation of all pkgs that depend on this change using nix-shell -p nox --run "nox-review wip"
• Tested execution of all binary files (usually in ./result/bin/)
• Fits CONTRIBUTING.md.