[Bug c/90476] prepossessor should error if #line 0

[egallager at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90476

--- Comment #4 from Eric Gallager <egallager at gcc dot gnu.org> ---
(In reply to Segher Boessenkool from comment #3)
> Where is it documented (in GCC). then?  I can't find it.

¯\_(ツ)_/¯

I dunno where they got that idea; just reporting it because I thought it seemed
like it might be relevant