Add protection from min/max macros

llvm-svn: 145407
diff --git a/libcxx/include/algorithm b/libcxx/include/algorithm
index 6749bf61..6255c52 100644
--- a/libcxx/include/algorithm
+++ b/libcxx/include/algorithm
@@ -595,6 +595,8 @@
 #include <iterator>
 #include <cstdlib>
 
+#include <__undef_min_max>
+
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #pragma GCC system_header
 #endif