Reviewed points

• package name fits guidelines (no change)
• package version fits guidelines (no change)
• package build on x86_64-linux
• executables tested on x86_64-linux
• all depending packages build

Notes on testing:

• Tested after rebasing onto current nixos-unstable channel (bc94dcf). Compared behaviour with lynx from current nixos-19.03.
• Opened https://en.wikipedia.org: With the executable from this pull request, the page looks like it looks with lynx from current nixos-19.03 channel. In particular, the colors have not changed.
• Opened https://en.wikipedia.org with and without -default_colors lynx command line option. With the option added, colors look more dim on my konsole terminal emulator, so the option apparently has an effect.

Comments

• There isn't much documentation (neither man page nor internet) about the default-colors option. From my observation, it has effects, but no negative effects. I can't judge if it is actually doing what it is supposed to do.
• Nevertheless, I can't see a problem with enabling this option.
• The lynx package has no maintainers. Notifying those that modified it recently: @dtzWill @jfrankenau
• I'm surprised that this change provokes so many rebuilds ("101-500"). lynx seems to be the base of a lot of other packages. From just grepping for "lynx" in <nixpkgs/pkgs> I get the vague impression that depending packages just use lynx to show some html to the user. If there are any users with a more involved usage (if lynx supports more at all), those packages should probably be checked more closely.

Thanks for the review @Yarny0. :) Looks like this is uncontroversial enough we can try it out in master.