Some more recursive include fixes/optimizations.

diff --git a/windows/scroll.c b/windows/scroll.c
index 46ec256..c20c485 100644
--- a/windows/scroll.c
+++ b/windows/scroll.c
@@ -8,7 +8,7 @@
  */
 
 #include <stdlib.h>
-#include "windows.h"
+#include "winuser.h"
 #include "class.h"
 #include "dc.h"
 #include "win.h"