Workaround for a problem with ifort 2018.1 and OpenMP.

Description

The Casida code crashes with ifort 2018.1 and OpenMP. Changing a pointer component into an allocatable seems to fix the problem, but I don't see anything wrong with the current version of the code. Most likely this is a compiler bug.

News snippet

Workaround for a problem with ifort 2018.1 and OpenMP.

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.