Update tex-unicode-math{,-doc} to 0.8f

- v0.8f (2017/08/02)

  * Emergency fix (thanks Bruno) for another bug revealed by `expl3` update.

- v0.8e (2017/07/30)

  * Add `\surd` to access the sqrt symbol.
  * Fix bug exposed by expl3 update to booleans.
  * Add Deja Vu Math TeX Gyre in list of symbols.
  * Add `\sime` alias for `\simeq` and `\nsimeq` for `\nsime`.
    (For negations it's helpful when they have consistent naming.)

(markd)