Description

Minor bugfixes:

The CG atan could fail for certain cases when alpha is zero
Debug=info was failing for dimensions lower than 3
The fallback on modified Gram-Schmidt was not robbust enough. The other method is more robust

News snippet

Minor bugfixes.

Checklist

I have checked that my code follows the Octopus coding standards
I have added tests for all the new features added in this request.