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/Lib/test/pickletester.py b/Lib/test/pickletester.py
index 5b9da56..42853c4 100644
--- a/Lib/test/pickletester.py
+++ b/Lib/test/pickletester.py
@@ -1,6 +1,9 @@
 import unittest
 import pickle
-import cPickle
+try:
+    import cPickle
+except ImportError:
+    cPickle = None
 import pickletools
 import copy_reg
 
@@ -10,7 +13,8 @@
 # Tests that try a number of pickle protocols should have a
 #     for proto in protocols:
 # kind of outer loop.
-assert pickle.HIGHEST_PROTOCOL == cPickle.HIGHEST_PROTOCOL == 2
+if cPickle is not None:
+    assert pickle.HIGHEST_PROTOCOL == cPickle.HIGHEST_PROTOCOL == 2
 protocols = range(pickle.HIGHEST_PROTOCOL + 1)