FT_Done_Stream(): do stream->close = 0 after calling stream->close(); this makes it safe to call FT_Done_Stream() more than once.

David: please review this; I hope you agree with this minor change.

src/base/ftobjs.c

@@ -297,7 +297,10 @@
   FT_EXPORT_FUNC( void )  FT_Done_Stream( FT_Stream  stream )
   {
     if ( stream && stream->close )
+    {
       stream->close( stream );
+      stream->close = 0;
+    }
   }