Reporting: Add missing file.

reporting/accuracy/has_cxx17_cmath.cpp

@@ -0,0 +1,18 @@
+//  Copyright John Maddock 2015.
+//  Use, modification and distribution are subject to the
+//  Boost Software License, Version 1.0. (See accompanying file
+//  LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
+
+#include <cmath>
+
+int main()
+{
+   long double d = 1;
+
+   d = std::erf(d);
+   d = std::erfc(d);
+   d = std::tgamma(d);
+   d = std::lgamma(d);
+   d = std::comp_ellint_1(d);
+   return d != 0 ? 0 : 1;
+}