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/test_exceptions.py b/Lib/test/test_exceptions.py
index be2cca1..0eb6b46 100644
--- a/Lib/test/test_exceptions.py
+++ b/Lib/test/test_exceptions.py
@@ -4,7 +4,11 @@
 import sys
 import unittest
 import warnings
-import pickle, cPickle
+import pickle
+try:
+    import cPickle
+except ImportError:
+    cPickle = None
 
 from test.test_support import TESTFN, unlink, run_unittest
 
@@ -292,6 +296,8 @@
 
                 # test for pickling support
                 for p in pickle, cPickle:
+                    if p is None:
+                        continue # cPickle not found -- skip it
                     for protocol in range(p.HIGHEST_PROTOCOL + 1):
                         new = p.loads(p.dumps(e, protocol))
                         for checkArgName in expected: