fileno not visible when -std=c++11 is used

[Florian Weimer]

* Arthur Schwarz:

> Win7 64-bit
> gcc 4.8.2 (cygwin)
>
> Ref:
> http://stackoverflow.com/questions/14172884/no-fileno-function-in-nuwen-net-
> mingw-distro

Cygwin or mingw?  Cygwin should have fileno because it approximates
POSIX.

Mingw probably has _fileno, following Microsoft's lead:

  <http://msdn.microsoft.com/en-us/library/zs6wbdhx.aspx>

Both approaches are fine because these environments have different
goals.  The GCC project likely does not care either way—it's a
library issue, not a compiler issue.