This PR makes several small improvements to the list/array/vector API:
* It fixes typos in `Init.Core`.
* It adds `List.isSome_min_iff` and `List.isSome_max_iff`.
* It adds `grind` and `simp` annotations to various previously
unannotated lemmas.
* It adds lemmas for characterizing `∃ x ∈ xs, P x` using indices as `∃
(i : Nat), ∃ hi, P (xs[i])`, and similar universally quantified lemmas:
`exists_mem_iff_exists_getElem` and `forall_mem_iff_forall_getElem`.
* It adds `Vector.toList_zip`.
* It adds `map_ofFn` and `ofFn_getElem` for lists/arrays/vectors.
This PR changes the "declaration uses 'sorry'" warning to use backticks
instead of single quotes, consistent with Lean's conventions for
formatting code identifiers in diagnostic messages.
This PR makes `mvcgen` produce deterministic case labels for the
generated VCs. Invariants will be named `inv<n>` and every other VC will
be named `vc<n>.*`, where the `*` part serves as a loose indication of
provenance.
This PR improves the API for invariants and postconditions and as such
introduces a few breaking changes to the existing pre-release API around
`Std.Do`. It also adds Markus Himmel's `pairsSumToZero` example as a
test case.
