fix for maildir synced tags in new.tags

[David Bremner]

David Bremner <david at tethera.net> writes:

> As I mentioned in [1], it's currently not possible to have maildir
> synced tags like 'flagged' in new.tags, which blocks some ideas about
> synching tags via maildir (in addition to just being a bug).
>
> This series fixes that. As I write this I remember that it doesn't
> bump the minor version of the SONAME, but that can always happen
> later.
>
> [1] id:20170804213845.18902-1-david at tethera.net

Anarcat has been running this series for some days with out complaining
so I guess I it probably doesn't cause catastrophic (meta-)data
loss. Discussion about the new API entry still welcome.
Series pushed.

d