[v3] more istream::ignore cleanups

[Paolo Carlini]

Benjamin Kosnik wrote:

>it is my understanding that max(), not some modulo,  was the imperfect
>solution that multiple people thought made the most sense in the
>(admittedly) corner case.
>
Are those discussions recorded somewhere? In the LWG reflector? I would  be
interested in the details: actually, strictly speaking, the whole LFS 
idea is not
compatible with the C++ standard in the present form...

> it's not great, but i think it at least
>signals what is going on for people who care to look.
>  
>
I'm not 100% sure, frankly: otherwise that would be a totally compelling 
argument!
It looks like you can end up ignoring <streamsize>::max chars also on a 
non-LFS
system, completely within the current standard. What's wrong with 
ignoring a whole
2G file till eof? (in principle, I mean, we are talking about 
corner-corner cases!)

Paolo.