[make E.Eval.strong handle EError properly.
John Meacham <john@repetae.net>**20060818070110] hunk ./E/Eval.hs 92
+    eval' ds (EError s ty) (t:rest) = do
+        nt <- eval' ds (EAp ty t) rest
+        return (EError s nt)
+    eval' ds e@EError {} [] = do return e