```
mail: Update Dovecot, Pigeonhole, fts-xapian
- Update mail/dovecot to 2.3.16
Changelog:
https://dovecot.org/pipermail/dovecot-news/2021-August/000463.html)
- Update mail/dovecot-pigeonhole to 0.5.16
Changelog:
https://dovecot.org/pipermail/dovecot-news/2021-August/000464.html)
Reviewed_by: ???
Differential_Revision: D31434
MFH: <branch|No> (<reason>)
```