G M:  Restore the ability for libcxx to compile again on mingw 64.

llvm-svn: 190837
diff --git a/libcxx/include/algorithm b/libcxx/include/algorithm
index e3b0882..367489f 100644
--- a/libcxx/include/algorithm
+++ b/libcxx/include/algorithm
@@ -631,6 +631,9 @@
 #if defined(__IBMCPP__)
 #include "support/ibm/support.h"
 #endif
+#if defined(_LIBCPP_MSVCRT) || defined(__MINGW32__)
+#include "support/win32/support.h"
+#endif
 
 #include <__undef_min_max>