[Bug fortran/53934] Better CPP macro diagnostics

[dominiq at lps dot ens.fr]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=53934
Bug 53934 depends on bug 44054, which changed state.

Bug 44054 Summary: Handle -Werror, -Werror=, -fdiagnostics-show-option, !GCC$ 
diagnostic (pragmas) and color
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=44054

           What    |Removed                     |Added
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             Status|NEW                         |RESOLVED
         Resolution|---                         |FIXED