short is not correctly set in Galoisfields

[gorzel]

In Galoisfields, the value of short is only set by the variables but not by the parameter.

> ring r8 =(8,a),x,dp;
>  a12*x2+a;
a5*x2+a
> ring r8xy = (8,a),(x,y),dp; 
>  a12*x2+a;
a5*x2+a
> ring r8x1x2 = (8,a),(x1,x2),dp;
>  a12*x2+a;
a^5*x2+a
> short;               // OK, here the value is controled by the variable
0
// -- Here short==0; is necessary by the choice of the parameter
> ring r8a1 = (8,a1),x,dp;
> short;                     // BUG it has to be 0 
1
>  a1^2*x2+a1;           // Input correct, but defalut output is errornous
a12*x2+a1
> short =0;
>  a1^2*x2+a1;
a1^2*x^2+a1