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

[Ed Smith-Rowland]

On 03/11/2016 10:55 AM, Jonathan Wakely wrote:
> The change approved in Jacksonville was to only add the special
> functions to <cmath> and not <math.h>
>
That's easy.
OK, since they changed that and the macro and made it nonconditional I 
should also drop the old-style macros __WANT_MATH_CANNEVERREMEMBER__ and 
the old-style version macro.
So, in other words, we're *not* actually supporting TR29124 (that's fine 
by me).
We can tweak the web pages.
People on C++11, C++14 can use tr1.

Did they keep the Cisms like:

   float
   foobarf(float x);

   double
   foobar(double x);

   long double
   foobarl(long double x);

I am keeping an eye out for the words of the draft github.
Maybe I'll ping Axel and Walter.

Ed