Fix PKG memory leak on {s.eval} corner-case

Make sure to correctly free the transformation data structures even when
parsed by {s.eval} at runtime, as opposed to one-time parsing during
startup, which would never highlight the leak:

    $var(proxy) = "$(du{nameaddr.uri}{re.subst,/scscf-int-/scscf-/})";
    $var(proxy) = $(var(proxy){s.eval});

Fixes #3233

(cherry picked from commit be764a1)

pvar.c

@@ -5006,6 +5006,9 @@ int pv_elem_free_all(pv_elem_p log)
 	{
 		t = log;
 		log = log->next;
+
+		if (t->spec.trans)
+			free_transformation((trans_t *)t->spec.trans);
 		pkg_free(t);
 	}
 	return 0;