`coding:' cookie in 21.1

`(xemacs)Recognize Coding' in 21.1 branch says:

>    You can specify the coding system for a particular file using the
> `-*-...-*-' construct at the beginning of a file, or a local variables
> list at the end.

But in fact xemacs does not handle `coding:' cookie.

Handling `coding:' was introduced in 21.2 branch (file-coding.c
(determine_real_coding_system)) back on 1999/09/01 06:34:32 and did
not change since 2000/03/29 18:40:51, so it looks quite `stable'.
However, it was never ported into stable branch.