GitLab

Also fixes pre-existing bug in iCombine error messages.

For half of #231.

This is a change enabling backward compatibility.

It now supports the specialization pattern `(H spat1 .. spatn)`, which first
recursively specializes the hypothesis `H` using the specialization patterns
`spat1 .. spatn`.

Thanks to @Blaisorblade for reporting.

pm_reduce just reduces away proof mode terms using cbv; pm_prettify just prettifies user-visible connectors using cbn.
Most uses of pm_default are converted to default to keep the desired reduction behavior.

List literals reduce with a spurious `emp` at the end, which is not pretty.

With a pretty proof by Robbert

make pm_maybe_wand a BI connective; reduce BI connectives and option combinators in the proofmode with cbn

We already do the same for the goal, this avoids some scope
delimiters being displayed.