Change magnover so magnitude of complex is real

[wlmb]

I followed a suggestion by Jörg Sommrey. The magnitude of integer vectors should be floating point, but that of complex vectors should be real. The actual float+ output specification yields complex magnitudes (with 0 imaginary part) for complex vectors. I guess the problem with the solution proposed here is that integer vectors may be converted to float vectors before the magnitude is computed, probably wasting space.

[coveralls]

coverage: 67.406%. remained the same
when pulling 3a04ab7 on wlmb:magnover
into 979060a on PDLPorters:master.