[Bug plugins/126882] [17 regression] -Wodr in callback-info.h vs plugin.cc

[pinskia at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=126882

--- Comment #2 from Drea Pinski <pinskia at gcc dot gnu.org> ---
callback_info in plugin.cc never gets exposed outside so wrap it in ana
anonymous namespace