Added configure test for const_cast<>(), and enabled it

for MSVC 5 and 6, and MinGW; use const_cast<>() in
wxConstCast if it is available.


git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@19537 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

acinclude.m4

@@ -580,3 +580,21 @@ if test "$enable_largefile" != no; then
     AC_MSG_RESULT($wx_largefile)
 fi
 ])
+
+
+dnl Available from the GNU Autoconf Macro Archive at:
+dnl http://www.gnu.org/software/ac-archive/htmldoc/ac_cxx_const_cast.html
+dnl
+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
+])