Try to reduce the nastiness that creeps in through Windows.h a bit.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@143816 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Driver/ToolChains.cpp b/lib/Driver/ToolChains.cpp
index c9e8633..3a404e5 100644
--- a/lib/Driver/ToolChains.cpp
+++ b/lib/Driver/ToolChains.cpp
@@ -43,10 +43,10 @@
 // Include the necessary headers to interface with the Windows registry and
 // environment.
 #ifdef _MSC_VER
-  #define WIN32_LEAN_AND_MEAN 1
+  #define WIN32_LEAN_AND_MEAN
+  #define NOGDI
+  #define NOMINMAX
   #include <Windows.h>
-  #undef min
-  #undef max
 #endif
 
 using namespace clang::driver;