[Bug c++/64079] %+D in diagnostics breaks pragma GCC diagnostic

[manu at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64079

--- Comment #12 from Manuel López-Ibáñez <manu at gcc dot gnu.org> ---
(In reply to Paolo Carlini from comment #11)
> Fixed.

Should we have a meta-bug for all uses of %+ that can potentially cause
problems or should we leave open this one as a catch all case? Removing even
one case would be an easy entry-level patch for new contributors, this is why I
marked it as a easy-hack.

I have also updated https://gcc.gnu.org/wiki/DiagnosticsGuidelines following
Jason's comments.