triu (Matlab function) Upper triangular part of a matrix

## Matlab/Scilab equivalent

Matlab | Scilab
    U = triu(A)
    U = triu(A, k)
    U = triu(A)
    U = triu(A, k)

Scilab and Matlab give different results if X is a String matrix. Then, use mtlb_triu instead.

Note that k can be complex in Matlab. In this case, only the real part of k is taken in account, while Scilab will yield an error.