Function: permorder
Section: combinatorics
C-Name: permorder
Prototype: G
Help: permorder(x): order of the permutation x.
Doc: given a permutation $x$ on $n$ elements, return its order.
 \bprog
 ? p = Vecsmall([3,1,4,2,5]);
 ? p^2
 %2 = Vecsmall([4,3,2,1,5])
 ? p^4
 %3 = Vecsmall([1,2,3,4,5])
 ? permorder(p)
 %4 = 4
 @eprog
