Store S.true/false (Basic instances) in Interval.left_open/right_open (fixes #6211)
UnXFAIL test for Reals
Fix test_printing.py
Raise NotImplementedError if left/right_open is not S.true/false
Merge pull request #2980 from skirpichev/3112-interval-make-basic-args

Store S.true/false in Interval.left_open/right_open