Make Win32's header file name lower for cross build on case-sensitive filesystem.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@124864 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Support/Windows/Windows.h b/lib/Support/Windows/Windows.h
index 6e0b585..dfa4be3 100644
--- a/lib/Support/Windows/Windows.h
+++ b/lib/Support/Windows/Windows.h
@@ -22,8 +22,8 @@
 #define WIN32_LEAN_AND_MEAN
 
 #include "llvm/Config/config.h" // Get build system configuration settings
-#include <Windows.h>
-#include <ShlObj.h>
+#include <windows.h>
+#include <shlobj.h>
 #include <cassert>
 #include <string>