[Bug preprocessor/61389] libcpp diagnostics shouldn't talk about ISO C99 for C++ input files

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61389

--- Comment #3 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Created attachment 33084
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=33084&action=edit
Adjust diagnostics according to language mode

To help translators this should replace whole strings not just pieces e.g.

   if (CPP_OPTION (pfile, cplusplus))
       cpp_error (pfile, CPP_DL_PEDWARN,
                  "ISO C++11 requires whitespace after the macro name");
   else
       cpp_error (pfile, CPP_DL_PEDWARN,
                  "ISO C99 requires whitespace after the macro name");