Improvements on ReadWriteLock, Object Statistics, and Seamless.
This version works on Pharo 7 and Pharo 8, but not in Pharo 9.
To changes at this level requires a lot of effort to keep the retro compatibility.
The main branch will be split into Pharo7, Pharo8, being the main branch supporting Pharo 9.
The fixes to work it on Pharo 9 will be done on the main branch.
This is the last tag with the master branch supporting Pharo 7/8/9.