[Bug preprocessor/116018] Feature request: #pragma GCC unpoison

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=116018

--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Note it is bad form to use `#pragma GCC poison` from a library's public header.
If there is any from a library's public header then those libraries should be
fixed.

GCC's plugin situtation is different and GCC's headers really should not be
always considered as a public header, it just happens that the plugins API for
GCC is every API and therefore there is no private headers.