Fix another ordering constraint with windows.h and comment about
a revers constraint that we got right (by chance).

llvm-svn: 304792
diff --git a/llvm/lib/DebugInfo/Symbolize/Symbolize.cpp b/llvm/lib/DebugInfo/Symbolize/Symbolize.cpp
index 57c818f..0561d6a 100644
--- a/llvm/lib/DebugInfo/Symbolize/Symbolize.cpp
+++ b/llvm/lib/DebugInfo/Symbolize/Symbolize.cpp
@@ -38,8 +38,10 @@
 #include <cstring>
 
 #if defined(_MSC_VER)
-#include <DbgHelp.h>
 #include <Windows.h>
+
+// This must be included after windows.h.
+#include <DbgHelp.h>
 #pragma comment(lib, "dbghelp.lib")
 
 // Windows.h conflicts with our COFF header definitions.