ac_cxx_const_cast

If the compiler supports const_cast<>, define HAVE_CONST_CAST.

AC_DEFUN([AC_CXX_CONST_CAST],
[AC_CACHE_CHECK(whether the compiler supports const_cast<>,
ac_cv_cxx_const_cast,
[AC_LANG_SAVE
 AC_LANG_CPLUSPLUS
 AC_TRY_COMPILE(,[int x = 0;const int& y = x;int& z = const_cast<int&>(y);return z;],
 ac_cv_cxx_const_cast=yes, ac_cv_cxx_const_cast=no)
 AC_LANG_RESTORE
])
if test "$ac_cv_cxx_const_cast" = yes; then
  AC_DEFINE(HAVE_CONST_CAST,,[define if the compiler supports const_cast<>])
fi
])