Fix a few minor formatting inconsistencies

* fix overlong lines
* where appropriate use %% instead of %
Use correct types for OTP >=17.x
Remove warnings_as_errors from rebar.config

rebar's beam files are actually compiled by bootstrap's call to
make:files/2, so warnings_as_errors in rebar.config isn't really used.
Fix typo s/of/on/
Merge branch 'minor-fixes' of https://github.com/tuncer/rebar into tuncer-minor-fixes
Merge branch 'tuncer-minor-fixes'