Bring the script out of the dark ages and into modern autoconfness.

llvm-svn: 16415
diff --git a/llvm/autoconf/m4/cxx_fwd_iterator.m4 b/llvm/autoconf/m4/cxx_fwd_iterator.m4
index 8da2944..73711b5 100644
--- a/llvm/autoconf/m4/cxx_fwd_iterator.m4
+++ b/llvm/autoconf/m4/cxx_fwd_iterator.m4
@@ -4,14 +4,12 @@
 [AC_CACHE_CHECK(whether the compiler has forward iterators,
 ac_cv_cxx_have_fwd_iterator,
 [AC_REQUIRE([AC_CXX_NAMESPACES])
-  AC_LANG_SAVE
-  AC_LANG_CPLUSPLUS
-  AC_TRY_COMPILE([#include <iterator>
+  AC_LANG_PUSH([C++])
+  AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[#include <iterator>
 #ifdef HAVE_NAMESPACES
 using namespace std;
-#endif],[forward_iterator<int,int> t; return 0;],
-  ac_cv_cxx_have_fwd_iterator=yes, ac_cv_cxx_have_fwd_iterator=no)
-  AC_LANG_RESTORE
+#endif]], [[forward_iterator<int,int> t; return 0;]])],[ac_cv_cxx_have_fwd_iterator=yes],[ac_cv_cxx_have_fwd_iterator=no])
+  AC_LANG_POP([C++])
 ])
 HAVE_FWD_ITERATOR=0
 if test "$ac_cv_cxx_have_fwd_iterator" = yes