Also, make our redefinition of done more robust under different
orders of Importing modules.

Since Coq 8.4 did not backtrack on eauto premises, we used to ensure
that hints like

  Hint Extern 0 (?x ≡{_}≡ ?y) => reflexivity.

were not used for goals involving evars by writing ?x ≡{_}≡ ?y instead
of _ ≡{_}≡ _.

This seems to be a legacy issue that no longer applies to Coq 8.5, so
I have removed these restrictions making these hints thus more powerful.

change statement of inv-open lemmas such that they do not force the invariant, and the 'inner step', to appear right next to each other

The rationale is that, just like the always lemmas about uPred and the frame-preserving updates for maps and iprdos, the versions with the ' are the "more specific" versions, hard-coding more assumptions in the shape of their conclusion.

thanks to Christian Doczkal <doczkal@ps.uni-saarland.de> for the Makefile snippet!

Also do some minor clean up.

tests.v is temporarily broken