Loopsimd alignment (Remerge)

This MR remerges !670 (merged), which was reverted due to to much time and memory requirement for looptest. This MR merges the branch again but with two changes:

• It adds explicit instantiations to the looptest
• It changes the default template argument of the alignment to 0, which means that it has no impact. In particular, if it is set to 0, rebound types have the template argument 0 as well. That reduces the number of types for that the tests are compiled and executed.

mentioned in merge request !782 (merged)

Thanks. Did you do some performance tests in ISTL? Does the change in rebind negatively affect the performance of solvers?

I just did some tests on sky and didn't found any performance differences.

merged

mentioned in commit e9837628