o Added unittest2 which has added the new features in unittest for Python 2.7

  backported to Python 2.3+.  Some of the features desired include better
  verbose reporting in unittest2.TextTestRunner and decorator support for
  skipping tests and expected failures.

  http://pypi.python.org/pypi/unittest2

o Modified the existing .py tests to use unittest2 and decorated
  TestSTL.test_step_into_stl(), which is known to always fail currently, with
  @unittest2.expectedFailure.

llvm-svn: 110397