fix Frege#357

Start of 3.25

corrected unification of generic type vars

From now on, it's 3.24

Merge pull request Frege#266 from homeworkprod/patch-1

A few improvements to the README.

Revert "restore backwards compatibility after changes for Frege#165"

This reverts commit 3f59987.

Starting point for release 23

Updated copyright year

Start of work on 3.22

make final compiler in 3 stages