[PATCH] Define iszero as a function template for C++ [BZ #20715]

[Joseph Myers]

On Fri, 21 Oct 2016, Florian Weimer wrote:

> Tested on x86_64, ppc64, ppc64le, s390x, aarch64.
> 
> I'm not sure if the new test is particularly meaningful, but at least it
> catches syntax errors in <math.h>.

This seems fine to me (with negative zero included in the testcase), and 
in accordance with how C++ defines bindings for C99 macros such as 
infinite.  I presume you're deliberately leaving it to future libstdc++ 
versions to handle the other is* macros from TS 18661-1 if they get into 
C2x and then into C++, as you haven't observed them causing problems for 
C++ code at present.

-- 
Joseph S. Myers
joseph@codesourcery.com