Log Message:
Update to FriCAS 1.2.6

Changse 1.2.6:

- Eigenvalues can be computed over larger range of base fields.
- Common denomiantor package handles now multivariate polynomials.
- More uniform break (error) handling.

Bug fixes, in particular:

- 'distribute' handles 'box' operator.
- Fixed problem with guessing over multivariate polynomilas.
- Fixed hashcode handling for Void in Aldor.