Add protection from min/max macros

llvm-svn: 145407
Cr-Mirrored-From: sso://chromium.googlesource.com/_direct/external/github.com/llvm/llvm-project
Cr-Mirrored-Commit: ab4f438239424dd39b83338ab0b4faa41245e506
diff --git a/include/string b/include/string
index 5f5a347..344bb55 100644
--- a/include/string
+++ b/include/string
@@ -446,6 +446,8 @@
 #include <cassert>
 #endif
 
+#include <__undef_min_max>
+
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #pragma GCC system_header
 #endif