[tz] Proposal: Sections for different kinds of backward links

[Paul Eggert]

On 11/14/21 04:16, Stephen Colebourne via tz wrote:

> The distinction between `obsolescent` and `other` seems unnecessary -
> they are all IDs no longer suitable for use.

We could merge the two into a single category 'obsolescent'.


> I need to be able to indicate which spelling users
> should use.

That info is already in zone.tab's column 3. Although that file is 
marked "deprecated", perhaps we can undeprecate it.