Add _eval_is_algebraic helpers for re/im/conjugate/abs

fixes #8656
Merge pull request #8699 from skirpichev/8656-fix

Add _eval_is_algebraic helpers for re/im/conjugate/abs
Add is_real functionality for factorial fix 8658
Merge pull request #8706 from aktech/issue8658

Add is_real functionality for factorial, Fix issue #8658