Paolo G. Giarrusso authored Nov 12, 2019 and Ralf Jung committed Nov 12, 2019

Revise following Iris `_CoqProject`
iris/iris@562501e6.

* Drop useless `-several-object-files`
* Add Coq 8.10 warnings.

Tested with Iris dev.2019-11-02.2.ea809ed4.