[Bug preprocessor/69126] [6 regression] _Pragma does not apply if part of a macro

[manu at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=69126

--- Comment #15 from Manuel López-Ibáñez <manu at gcc dot gnu.org> ---
(In reply to Paolo Carlini from comment #2)
> the regression and I'm pretty sure would not introduce other wrt the status
> pre-r226234, but I don't fully understand why that is necessary, there are

Wasn't the reason for removing '+' a bug report showing a similar case (#pragma
diagnostic being ignored because '+' does not affect the pragma)? 

Cases that did work before but don't work now just worked by chance. Unrelated
changes to input_location would also break them.

David's fix is a step in the right direction.