C/C++ standards supported by the preprocessor

[Sandra Loosemore]

I noticed that the section on preprocessor options in the GCC manual 
(which is also shared by the CPP manual) still claims that the default 
-std= values are gnu90 for C and gnu++98 for C++, and does not list  any 
C++ versions after gnu++98.  AFAICT from digging through code and trying 
some experiments to see what's accepted on the command line, the options 
and defaults for CPP are exactly the same as those for GCC; is that correct?

I'd like to get rid of the duplicate documentation, somehow -- having to 
maintain two copies can only lead to more problems with them getting out 
of sync in the future, plus the GCC manual already lists so many options 
we don't need to list some of them twice.

-Sandra