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

diff --git a/dlls/urlmon/urlmon_main.h b/dlls/urlmon/urlmon_main.h
index d34597e..be39cef 100644
--- a/dlls/urlmon/urlmon_main.h
+++ b/dlls/urlmon/urlmon_main.h
@@ -19,7 +19,10 @@
 #ifndef __WINE_URLMON_MAIN_H
 #define __WINE_URLMON_MAIN_H
 
+#include <stdarg.h>
+
 #include "windef.h"
+#include "winbase.h"
 
 extern HINSTANCE URLMON_hInstance;