Code divergence of real/complex CPU part in trans_ev_band_to_full
The real/complex CPU parts of trans_ev_band_to_full diverged:
The real code path uses blocking, the complex part does not!
- make blocking in real part an OPTION, i.e. a fall back to same code path as the complex version should be possible
- implement blocking for complex part also OPTIONAL.
In this way, we retain better tuning options for different architectures