gcd calculation
[pgcd,U]=gcd(p)
computes the gcd of components of p and a unimodular matrix (with polynomial inverse) U, with minimal degree such that
p*U=[0 ... 0 pgcd]
//polynomial case
s=`poly`_(0,'s');
p=[s,s*(s+1)^2,2*s^2+s^3];
[pgcd,u]=gcd(p);
p*u
//integer case
V=`int32`_([2^2*3^5, 2^3*3^2,2^2*3^4*5]);
[thegcd,U]=gcd(V)
V*U