IDs - uniqueness for inline only within segments (A)

[Yves Savourel <ysavourel@enlaso.com>]

Hi David, all,

> *A)*
> Uniqueness of inline used ids is currently only enforced within a segment,
> which is clearly wrong and there is an easy fix.
> *Proposed Solution: Enforce inline id uniqueness within <unit>*

I believe the original intent was to have uniqueness within the <unit>. For example see the PR for adding inline codes: "The id
value of the added code MUST be different from all id values in both source and target content of the unit where the new code is
added."

But obviously not all PRs that.
So I certainly support the changes to make sure we have uniqueness of id within the unit rather than segment.

-yves