patch 8.0.0281: some files are still using ARGSUSED instead of UNUSED

Problem:    MS-Windows files are still using ARGSUSED while most other files
            have UNUSED.
Solution:   Change ARGSUSED to UNUSED or delete it.

src/os_w32exe.c

@@ -38,13 +38,12 @@ void _cdecl SaveInst(HINSTANCE hInst);
 static void (_cdecl *pSaveInst)(HINSTANCE);
 #endif
 
-/*ARGSUSED*/
     int WINAPI
 WinMain(
-    HINSTANCE	hInstance,
-    HINSTANCE	hPrevInst,
+    HINSTANCE	hInstance UNUSED,
+    HINSTANCE	hPrevInst UNUSED,
     LPSTR	lpszCmdLine,
-    int		nCmdShow)
+    int		nCmdShow UNUSED)
 {
     int		argc = 0;
     char	**argv;