Function: algpow
Section: algebras
C-Name: algpow
Prototype: GGG
Help: algpow(al,x,n): element x^n in al.
Doc: Given an element $x$ in \var{al} and an integer $n$, computes the
 power $x^n$ in the algebra \var{al}.
 \bprog
 ? A = alginit(nfinit(y), [-1,-1]);
 ? algpow(A,[1,1,0,0]~,7)
 %2 = [8, -8, 0, 0]~
 @eprog

 Also accepts a square matrix with coefficients in \var{al}.
