ac_cxx_have_numeric_limits

If the compiler has numeric_limits<T>, define HAVE_NUMERIC_LIMITS.

AC_DEFUN([AC_CXX_HAVE_NUMERIC_LIMITS],
[AC_CACHE_CHECK(whether the compiler has numeric_limits<T>,
ac_cv_cxx_have_numeric_limits,
[AC_REQUIRE([AC_CXX_NAMESPACES])
 AC_LANG_SAVE
 AC_LANG_CPLUSPLUS
 AC_TRY_COMPILE([#include <limits>
#ifdef HAVE_NAMESPACES
using namespace std;
#endif],[double e = numeric_limits<double>::epsilon(); return 0;],
 ac_cv_cxx_have_numeric_limits=yes, ac_cv_cxx_have_numeric_limits=no)
 AC_LANG_RESTORE
])
if test "$ac_cv_cxx_have_numeric_limits" = yes; then
  AC_DEFINE(HAVE_NUMERIC_LIMITS,,[define if the compiler has numeric_limits<T>])
fi
])