Since `fresh_generic` is too inefficient for all practical purposes, we seal
off its definition. That way, Coq will not accidentally unfold it during
unification or other tactics.

This issue actually occurred in iGPS, as reported by Hai.

silence fewer warnings, add comment about overwriting notation

See merge request !49

fix λ.. printing and test it

See merge request !51

Make trivial instances explicit

See merge request !50

This is in preparation for coq/coq#9274.

`tc_to_bool` to turn a type class into a Boolean that expresses if there is an instance

See merge request !48

Add results about deleting and inserting filtered out elements

See merge request !46

Get rid of the awk.Makefile references

See merge request !47

Two reasons:

- The equality makes it very hard to use the lemma with `rewrite`.
- The version for lists `insert_zip_with` does not have the equality either.