fetch does not work for lists of type alias

[steenpass]

> proc p1(alias list j)
. {
.     def br = basering;
.     ring s = 0, x, ds;
.     list k = fetch(br, j);
.     setring(br);
. }
> ring r = 0, x, dp;
> list l = list(ideal(x));
> p1(l);
   ? identifier j not found in br
   ? error occurred in or before ::p1 line 4: `    list k = fetch(br, j);`
   ? leaving ::p1
   skipping text from `;` error at token `)`
> 

This seems to be related to:

​http://www.singular.uni-kl.de:8002/trac/ticket/668

The differences are:

• Here, the object is a list and not an ideal.
• The list has a different identifier inside the procedure than on top-level ('j' vs. 'l').

[hannes]

fixed with e3e12979d70ffe1c897b47e9826594e9099b886a