Explicitly use core hint database

See merge request !43

Adding a hint without a database now triggers a deprecation warning in
Coq master (https://github.com/coq/coq/pull/8987).

- Interaction with delete
- Make name about map interacting with insert consistent.

MR #41 relies on https://github.com/coq/coq/issues/5039, which has
not been fixed in Coq 8.6.

Consistently block `simpl` on all `Z` operations

See merge request iris/stdpp!41

This makes some proress on #21. Still, the question remains if a more
generic solution exists.

TIMED is still supported

Add `Countable` instance for `gset`.

See merge request robbertkrebbers/coq-stdpp!40

begin a test suite

See merge request robbertkrebbers/coq-stdpp!39