Link to a tiny patch to libstdc++-4.7 to work around the <chrono> issues

from the C++ status page.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@154890 91177308-0d34-0410-b5e6-96231b3b80d8

www/cxx_status.html

@@ -40,8 +40,9 @@
 
 <p>You can use Clang in C++11 mode either
 with <a href="http://libcxx.llvm.org/">libc++</a> or with gcc's libstdc++.
-libstdc++-4.4 requires <a href="libstdc++4.4-clang0x.patch">a patch</a> to work
-with clang; other versions have not been tested.</p>
+Patches are needed to make <a href="libstdc++4.4-clang0x.patch">libstdc++-4.4</a>
+and <a href="libstdc++4.7-clang11.patch">libstdc++-4.7</a> work with Clang in
+C++11 mode.</p>
 
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www/libstdc++4.7-clang11.patch

@@ -0,0 +1,13 @@
+Index: include/std/type_traits
+===================================================================
+--- include/std/type_traits	(revision 185724)
++++ include/std/type_traits	(working copy)
+@@ -1746,7 +1746,7 @@
+ 
+   template<typename _Tp, typename _Up>
+     struct common_type<_Tp, _Up>
+-    { typedef decltype(true ? declval<_Tp>() : declval<_Up>()) type; };
++    { typedef typename decay<decltype(true ? declval<_Tp>() : declval<_Up>())>::type type; };
+ 
+   template<typename _Tp, typename _Up, typename... _Vp>
+     struct common_type<_Tp, _Up, _Vp...>