C++11 math overloads in <math.h> on Solaris

[Jonathan Wakely]

Hi Rainer,

Could you tell me whether the <math.h> on Solaris declares the
additional overloads such as acosh(float) and acosh(long double) in
C++98 mode, or only for C++11 and later?

I'm trying to fix and simplify <tr1/cmath> for PR 69893 and I think we
can get rid of most of the __CORRECT_ISO_CPP11_MATH_H_PROTO conditions
if we do it like this:

namespace std { namespace tr1 {

  // For functions defined in C++03 the additional overloads are already
  // declared in <cmath> so we can just re-declare them in std::tr1.

  using std::acos;
  using std::asin;
  // etc. ...

#if __cplusplus >= 201103L

  // Since C++11, <cmath> defines additional overloads for these functions
  // in namespace std.

  using std::acosh;
  using std::asinh;
  // etc. ...

#else // ! C++11

  // In C++03 we need to provide the additional overloads.

#ifndef __CORRECT_ISO_CPP11_MATH_H_PROTO
   inline float
   acosh(float __x)
   { return __builtin_acoshf(__x); }

   inline long double
   acosh(long double __x)
   { return __builtin_acoshl(__x); }
#endif
 
   template<typename _Tp>
     inline typename __gnu_cxx::__enable_if<__is_integer<_Tp>::__value, 


The __CORRECT_ISO_CPP11_MATH_H_PROTO isn't needed here if Solaris only
provides float and long double overloads for acosh, asinh, atanh,
cbrt, copysign etc.  when __cplusplus >= 201103L.