Optimisation : do nothing for content types with no cck fields ?

Contrary to 4.7 version where there was a distinct line between cck-handled content-types and others, 5.0 cck can potentially act upon any content type.

It plugs on hook_nopeapi and hook_form_alter to manage fields and generate forms.
Those hooks are executed for all content types, and

This could probably be optimized for most of the ops (if not all ?) by checking first in content_nodeapi and content_form_alter that the content type has fields, and doing plain nothing if it has none.

This should probably be done after the forthcoming release, though.