smb: Fix stack smashing

It is described on http://shinnai.altervista.org/exploits/SH-008-20101026.html
Thanks to geal for helping finding the problem
(cherry picked from commit b531955c)
Signed-off-by: Rafaël Carré <rafael.carre@gmail.com>

modules/access/smb.c

@@ -363,7 +363,7 @@ static void Win32AddConnection( access_t *p_access, char *psz_path,
                                 char *psz_user, char *psz_pwd,
                                 char *psz_domain )
 {
-    DWORD (*OurWNetAddConnection2)( LPNETRESOURCE, LPCTSTR, LPCTSTR, DWORD );
+    DWORD WINAPI (*OurWNetAddConnection2)( LPNETRESOURCE, LPCTSTR, LPCTSTR, DWORD );
     char psz_remote[MAX_PATH], psz_server[MAX_PATH], psz_share[MAX_PATH];
     NETRESOURCE net_resource;
     DWORD i_result;