Revert "BUGFIX: use a more widely compatible version of sadd"
This reverts commit aa577f11fd5cb736c4904e47ba88c9ebb08e974a.
I think the compatibility might not be a problem anymore, after 8 years? 😃
This reduces chances of errors where consumers of strings mutate inputs
and reduces memory usage of the app.
Test suite passes now, but there may be some stuff left, so we will run
a few sites on a branch prior to merging
