Remove ^L characters hidden randomly in the code. Not those used in text files as delimiters.

While working on a tool that processes Erlang code and testing it against this repo,
I found out about those little sneaky 0xff. I thought it may be of help to other
people build such tools to remove non-conforming-to-standard characters.
Merge branch 'fenollp/treewide_remove_unexpected_0xff/OTP-11323' into maint

* fenollp/treewide_remove_unexpected_0xff/OTP-11323:
  Remove ^L characters hidden randomly in the code. Not those used in text files as delimiters.
Merge branch 'maint'
Support named funs in the debugger interpreter

The current code for the evaluation of ordinary funs is dependent
on the order on variables in the fun environment as returned by
erlang:fun_info(Fun, env). As it happened, adding the code for
named funs changed the order in the environment for ordinary funs.

To avoid the problem in the future, make sure that we only have one
free variable in the funs that we will need to inspect using
erlang:fun_info(Fun, env).
Test named funs