Quite a few fixes to make the library and test suite more robust when
cPickle cannot be imported.  This was necessary because my last mass
checkin broke cPickle and I don't feel like debugging it right now;
but it seems a good idea in general not to require cPickle when
pickle.py is also there.  A few unrelated fixes for issues while
debigging various test failures.

setup.py: disable building of cPickle until I've fixed it

Objects/...

  genobject.c: disallow raising string exceptions

Lib/...

  Cookie.py: fix doctest not to fail if cPickle is missing
  ctypes/macholib/dyld.py: fix relative imports
  sqlite3/__init__.py: fix relative import
  xml/dom/__init__.py: fix relative import

Lib/test/...

  regrtest.py: reduce list of skipped items on darwin

  test_generators.py: don't test string exceptions; test throw() errors
  test_traceback.py: don't test string exceptions

  pickletester.py: don't fail if cPickle is missing
  test_datetime.py: don't fail if cPickle is missing
  test_descr.py: don't fail if cPickle is missing (still some other failures)
  test_exceptions.py: don't fail if cPickle is missing
  test_re.py: don't fail if cPickle is missing

  test_array.py: use pickle, not cPickle
  test_bool.py: don't fail if cPickle is missing
  test_deque.py: use pickle, not cPickle
  test_logging.py: use pickle, not cPickle
diff --git a/Objects/genobject.c b/Objects/genobject.c
index 4d0c4f6..bad485c 100644
--- a/Objects/genobject.c
+++ b/Objects/genobject.c
@@ -253,12 +253,11 @@
 		}
 	}
 
-	/* Allow raising builtin string exceptions */
-
-	else if (!PyString_CheckExact(typ)) {
+	else {
 		/* Not something you can raise.  throw() fails. */
 		PyErr_Format(PyExc_TypeError,
-			     "exceptions must be classes, or instances, not %s",
+			     "exceptions must be classes or instances "
+			     "deriving from BaseException, not %s",
 			     typ->ob_type->tp_name);
 			goto failed_throw;
 	}