Fixed header dependencies to be fully compatible with the Windows
headers (with help from Dimitrie O. Paun).

windows/winhelp.c

diff --git a/windows/winhelp.c b/windows/winhelp.c
index 6f5e3c0..7dc9c63 100644
--- a/windows/winhelp.c
+++ b/windows/winhelp.c
@@ -22,12 +22,14 @@
 #include "config.h"
 
 #include <stdlib.h>
+#include <stdarg.h>
 #include <stdio.h>
 #include <string.h>
 #ifdef HAVE_UNISTD_H
 # include <unistd.h>
 #endif
 #include "wine/debug.h"
+#include "windef.h"
 #include "winbase.h"
 #include "wingdi.h"
 #include "winuser.h"