case H; clear H would fail when H is dependent whereas destruct H
would succeed on that, but just not clear it.

The case tactic is faster than destruct.

Example:

Goal
  ¬False → ¬False → ¬False → ¬False → ¬False → ¬False → ¬False →
  False.
Proof.
  intros. done. (* takes very long *)

Add locking to value-scope notation for lambdas

This attempts to hide all our locking machinery so that users don't have to care. To this end, `locked` is added to the value-scope notation for lambdas and recursive functions, and the tactics wp_rec and wp_lam are enhanced to unlock properly.

The main open question is: How can we figure out automatically what to unfold? The heuristic I cam up with fails in barrier_client because there, we have a value parameterized by something on the Coq level.

Maybe a more viable alternative would be to add locking to the coercion that embeds values into expressions?

Cc @robbertkrebbers @jjourdan

See merge request !34

This reverts commit b115ff3f.

Update a comment in cmra_big_op.v

fixes a small typo in the comments

See merge request !33