bug#10650: view-mode inconsistencies wrt special mode-class

[Juri Linkov]

> Why do we even care about not entering view-mode in special mode buffers
> anyway? If you don't want view-mode, don't ask for it.
> Is there any motivation for this feature beyond "some guy likes to press
> v on everything in dired, then complain when he gets what he asked for"?

Not just pressing v in dired, but also other cases like visiting a read-only
"special" file when `view-read-only' is non-nil, or typing `C-x C-q C-x C-q'
(both cases are handled in files.el)

Such special modes as image-mode and archive-mode don't need to activate
`view-mode' because in fact they are already "view" modes (as opposed to
"edit" modes with enabled self-inserting commands) and they bind own
keys to "view" their special (i.e. not plain text) content.