improved accidental handling in auto-header ready for master

Folks,


please test

  https://gitlab.freedesktop.org/freetype/freetype/-/merge_requests/356

and report whether you see strange behaviour; I'm going to push this
in a few days.

I'm already working on various follow-ups to further improve handling
of diacritics (for example, handling 'ő' and 'ᾷ').


    Werner