zlangb(3) on Linux
The text 8e95a4d169f3, as Debian 4.0 (Etch), Debian 3.1 (Sarge) shipped it.
return the value of the one norm, or the Frobenius norm, or the infinity norm, or the element of largest absolute value of an n by n band matrix A, with kl sub-diagonals and ku super-diagonals