Fesom2.5 intel fixes

[trackow]

Test to see it worked...

[JanStreffing]

@trackow Does this still make sense to merge for 2.6?

[JanStreffing]

@trackow Any update on this PR?

[trackow]

The io_meandata.F90 changes by Dima and the added k-loop in oce_fer_gm.F90 I don't know what they are for, but we should check with him @dsidoren .

 !Intel vectorisation did something strange in the above lines hence we had to code it more explicitely
        nzmax=mesh%nl
        nzmin=1
        do k=1, nod_in_elem2D_num(n)
           nzmax=min(nzmax, nlevels(nod_in_elem2D(k, n)))
           nzmin=max(nzmin, ulevels(nod_in_elem2D(k, n)))
        end do

The rest, for example, MPI_BARRIERs and OMP barriers I would not touch as they worked well in https://github.com/FESOM/fesom2/tree/2.5.0.3_de. So would again suggest to just merge that branch instead

[JanStreffing]

We leave this open until after merge of #571 and check what's left then. @patrickscholz said the io_meandata changes might be good still and not covered elsewhere.