Improve evaluation of relationals with -oo if "other" arg is positive

fixes #8449
Merge pull request #8460 from skirpichev/8449-fix

Improve evaluation of relationals with -oo if "other" arg is nonnegative
Add code quality test for self assignments (fixes #8362)
Code quality: don't assign to self (issue #8362)
Fix remaining self assignments
Fix py3-incompatible code
py3 fix for mailmap_update.py
Code quality: don't assign to cls (classmethod's)