[NTG-context] set_lua freezes control sequences

[Marcel Fabian Krüger]

Hi,

I noticed that recent LuaMetaTeX versions treats control sequences
defined using token.set_lua with `value` or `condition` as frozen and
does not allow redefining them. Given that these are not macros, we also
can't "unfreeze" them using \unletfrozen.

  1. Would it be possible to add a variant of Lua value and condition
  control sequences that are not frozen?

  2. Also is there some way to disable the \frozen restrictions
  altogether? Maybe \suppressfrozenerror?

  3. I also noticed that `token.set_lua` is not affected by control
  sequences being frozen. Therefore it allows redefining frozen
  control sequences which seems inconsistent.

Best regards,
Marcel