viper-mode C-[ behavior change in Emacs 24.4

[iquiw <iku.iwasa@gmail.com>]

Hi,

I'm using "C-[" key as ESC key in viper-mode, i.e. to escape from
viper insert mode.
It works on Emacs 24.3, but not on Emacs 24.3.92.
Typing "C-[" just displays "ESC-" in minibuffer on Emacs 24.3.92.

I found a workaround, evaluating the following code (from
viper-catch-tty-ESC) gives expected behavior.

```
(let ((esc-binding (viper-uncatch-tty-ESC)))
    (define-key input-decode-map
      [?\e] `(menu-item "" ,esc-binding :filter viper--tty-ESC-filter)))
```

I would like to know proper way to achieve the behavior.

Thanks in advance.