Added missing includes to avoid warnings/errors.

diff --git a/server/file.c b/server/file.c
index 3c5e816..e624998 100644
--- a/server/file.c
+++ b/server/file.c
@@ -18,7 +18,7 @@
 #include <utime.h>
 
 #include "winerror.h"
-#include "winnt.h"
+#include "winbase.h"
 #include "server/thread.h"
 
 struct file