[libcxx] Set _LIBCPP_ELAST for mingw.

Reviewers: K-ballo, mclow.lists, EricWF

Reviewed By: EricWF

Subscribers: jfb, jroelofs, majnemer, cfe-commits

Differential Revision: http://reviews.llvm.org/D6558

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@225273 91177308-0d34-0410-b5e6-96231b3b80d8
(cherry picked from commit 656850f03e)

Change-Id: I97d6e6a2f4613f9f618cbec4ba7122699f572a47

src/ios.cpp

@@ -10,15 +10,18 @@
 #include "__config"
 
 #include "ios"
-#include "streambuf"
-#include "istream"
-#include "string"
+
+#include <stdlib.h>
+
 #include "__locale"
 #include "algorithm"
+#include "config_elast.h"
+#include "istream"
+#include "limits"
 #include "memory"
 #include "new"
-#include "limits"
-#include <stdlib.h>
+#include "streambuf"
+#include "string"
 
 _LIBCPP_BEGIN_NAMESPACE_STD