Add C++ special math functions to C++17

[Tobias Burnus]

Ed Smith-Rowland wrote:
> --- include/bits/specfun.h	(svn+ssh://emsr@gcc.gnu.org/svn/gcc/trunk/libstdc++-v3/include)	(working copy)
> +++ svn+ssh://emsr@gcc.gnu.org/svn/gcc/trunk/libstdc++-v3/include	(revision 234098)
> @@ -1,6 +1,6 @@
>  // Mathematical Special Functions for -*- C++ -*-
>  
> -// Copyright (C) 2006-2016 Free Software Foundation, Inc.
> +// Copyright (C) 2006-2015 Free Software Foundation, Inc.

The patch looks reversed ("---" for the "working copy", copyright-year change reversed etc.)

Cheers,

Tobias