[CHORE] Remove legacy code from comments

[jgabaut]

Situation

A lot of legacy code is embedded as comment and it's an eyesore.
Removing it is due, but also a chore.

Maybe we should extract it to some "legacy docs" .c file that can be translated with doxygen, so the old code still retains some meaning.

Steps

• Add a legacy_docs.c file to hold meaningful definitions that would be nice to parse with doxygen.

• Blame legacy commented sections, looking for the big ones.

  • For all important ones:
  • Add info about the last tag to use this legacy section to the relevant legacy_docs.c part
  • Add this legacy section to legacy_docs.c either as a function printing the legacy source code snippets, or as a single string constant.
  • Open a PR

[jgabaut]

Merging this would also need the eventual Github Pages deploy to account for the legacy code at some point. See #50.