Equivalence table between C++ and C file open modes

[Martin Sebor]

Paolo Carlini wrote:
> Paolo Carlini wrote:
> 
>> I'm committing the below to mainline.
> 
> Actually, this version, which seems more clear and puts at the end the 
> lines new wrt C++03 (at some point we may add more...)

There's also ios::app alone (soon to be added to issue 596) which
traditionally translates to "a", and ios::app|ios::in which is
equivalent to "a+". I think libstdc++ accepts both.

Martin