[PATCH v4 02/14] box: introduce key_def_parts_are_sequential

[Vladimir Davydov]

On Thu, Oct 11, 2018 at 10:58:47AM +0300, Kirill Shcherbatov wrote:
> Introduced a new key_def_parts_are_sequential routine that test,
> does specified key_def have sequential fields. This would be
> useful with introducing JSON path as there would be another
> complex criteria as fields with JSONs can't be 'sequential' in
> this meaning.
> 
> Part of #1012.

Again, should be

Needed for #1012

Other than that, the patch looks OK to me.