Add protection from min/max macros

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@145407 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/include/bitset b/include/bitset
index c970f32..4735754 100644
--- a/include/bitset
+++ b/include/bitset
@@ -129,6 +129,8 @@
     #include <cassert>
 #endif
 
+#include <__undef_min_max>
+
 _LIBCPP_BEGIN_NAMESPACE_STD
 
 template <size_t _N_words, size_t _Size>