Log Message:
tex-unicode-math{,-doc}: update to 0.8r

* Revise definitions of `\setminus` and `\smallsetminus`
  — long overdue.
  Note that there are compatibility considerations with this change.

* Add `\diagup` and `\diagdown`

* Make `\operator at font` protected to allow operators
  (e.g., `\cos`) in section headings (etc).

* Allow `\symcal` to handle lowercase Latin.

* Add additional fonts to the symbol listing document