[Patch] Fix libstdc++/7744

[Paolo Carlini]

Nathan Myers wrote:

>My only remark on this round is that, again, I am uncomfortable with 
>overloading standard member names.  I'd rather see a _M_ prefix on 
>those, at least.
>
Ok, Nathan (*) and Gaby.

In order to facilitate mine and pending Benjamin commits, the posted
version is already in. But I promise to do the change in the next
few days.

Just to be sure: you prefer, for instance:

   __basic_file<char>::_M_xsgetn(char* __s, streamsize __n)

right?

Paolo.

(*) Nathan, basing a comment of yours of a few days ago I had believed
this was not really an issue:

 http://gcc.gnu.org/ml/libstdc++/2003-03/msg00031.html

In particular:

> > >Finally, mustn't these members' names be uglified, e.g. _M_no_block
> > >etc.?
> > >
> > The other members of __basic_file<char> aren't and I followed the
> > existing practice. Should we change all of them?
>
> Oops, sorry, I confused myself for just long enough to post.