vorepository: use vlc_MakeTmpFile (thus mkstemp) instead of tempnam

resolves warning about insecure function

modules/misc/addons/vorepository.c

@@ -400,20 +400,10 @@ static int Retrieve( addons_finder_t *p_finder, addon_entry_t *p_entry )
         FREENULL( p_finder->p_sys->psz_tempfile );
     }
 
-    p_finder->p_sys->psz_tempfile = tempnam( NULL, "vlp" );
-    if ( !p_finder->p_sys->psz_tempfile )
-    {
-        msg_Err( p_finder, "Can't create temp storage file" );
-        vlc_stream_Delete( p_stream );
-        return VLC_EGENERIC;
-    }
-
-    int fd = vlc_open( p_finder->p_sys->psz_tempfile,
-                       O_WRONLY | O_CREAT | O_EXCL, 0600 );
+    int fd = vlc_MakeTmpFile(&p_finder->p_sys->psz_tempfile, PACKAGE_NAME"-vlp.XXXXXX", NULL);
     if( fd == -1 )
     {
-        msg_Err( p_finder, "Failed to open addon temp storage file" );
-        FREENULL(p_finder->p_sys->psz_tempfile);
+        msg_Err( p_finder, "Can't create temp storage file" );
         vlc_stream_Delete( p_stream );
         return VLC_EGENERIC;
     }