removed implication that unsafe pointers are automatically untraced

clarification: "UNSAFE" means that a pointer is compatible to address and can be freely set. Does not imply "UNTRACED"
"UNTRACED" means a pointer is not traced by the garbage collector. Most (but not necessarily all -- cf. cooperative kernel) unsafe pointers are untraced.

git-svn-id: https://svn.inf.ethz.ch/svn/lecturers/a2/trunk@7472 8c9fc860-2736-0410-a75d-ab315db34111

source/FoxSyntaxTree.Mod

@@ -1384,7 +1384,7 @@ TYPE
 		END IsPointer;
 		
 		PROCEDURE NeedsTrace*(): BOOLEAN;
-		BEGIN RETURN ~isUnsafe & ~isUntraced;
+		BEGIN RETURN  ~isUntraced;
 		END NeedsTrace;
 
 		PROCEDURE Accept*(v: Visitor);