#23 Fix for null DCG rules

[Glendon Holst]

The following does not compile on JLog 1.3.6 (represents a null terminal):

s --> [].

This code change to jDCG.makeDCGBaseCompoundTerm in jDCG.java add support for a Null List in the DCG:

250c250,257
< if (rt instanceof jListPair)

---

if (rt instanceof jNullList)
{jUnify un;

terms.addTerm(un = new jUnify());

pr.addElement(new dcgUnifyPredicateUpdate(un));
}
else if (rt instanceof jListPair)
382c389
<

---

Fix will appear in next version of JLog