Missing strtold()

[ksdhans]

Clib2 is missing the strtold() function.

This is resulting in our GCC not having std::strtoi(), etc., because the GCC configuration scripts fail the C99 stdlib test below:

# Check for the existence in <stdlib.h> of lldiv_t, et. al.
AC_MSG_CHECKING([for ISO C99 support in <stdlib.h> for C++11])
AC_CACHE_VAL(glibcxx_cv_c99_stdlib_cxx11, [
  GCC_TRY_COMPILE_OR_LINK(
    [#include <stdlib.h>
     volatile float f;
     volatile long double ld;
     volatile unsigned long long ll;
     lldiv_t mydivt;],
    [char* tmp;
     f = strtof("gnu", &tmp);
     ld = strtold("gnu", &tmp);
     ll = strtoll("gnu", &tmp, 10);
     ll = strtoull("gnu", &tmp, 10);
     ll = llabs(10);
     mydivt = lldiv(10,1);
     ll = mydivt.quot;
     ll = mydivt.rem;
     ll = atoll("10");
     _Exit(0);
    ], [glibcxx_cv_c99_stdlib_cxx11=yes], [glibcxx_cv_c99_stdlib_cxx11=no])
])
AC_MSG_RESULT($glibcxx_cv_c99_stdlib_cxx11)
if test x"$glibcxx_cv_c99_stdlib_cxx11" = x"yes"; then
  AC_DEFINE(_GLIBCXX11_USE_C99_STDLIB, 1,
    [Define if C99 functions or macros in <stdlib.h> should be imported
    in <cstdlib> in namespace std for C++11.])
fi

[ksdhans]

I hit this problem again. Missing bits like this make C++ code less usable, because key parts end up missing.

It should be relatively easy to add, because a long double and double are the same size (i.e., just redirect to strtod()).