Make sure that match_hostname and CertificateError are available in Python 3.1

distlib doesn't seem to support Python 3.0 and Python 3.1 (the tests raise an exception), so I recognize that you might reject this.

The reason I submitted this is because `pip` vendors this library and this would hopefully allow `pip` to work with Python 3.1 without the monkeypatching that I proposed in https://github.com/pypa/pip/pull/1227

```
(py31.venv)marca@marca-mac:~/dev/hg-repos/distlib$ python -V
Python 3.1.4
(py31.venv)marca@marca-mac:~/dev/hg-repos/distlib$ python -c 'import distlib.compat; print(distlib.compat.match_hostname)'
Traceback (most recent call last):
  File "<string>", line 1, in <module>
  File "distlib/compat.py", line 140, in <module>
    from ssl import match_hostname, CertificateError
ImportError: cannot import name match_hostname
(py31.venv)marca@marca-mac:~/dev/hg-repos/distlib$ hg update py31_1
resolving manifests
getting distlib/compat.py
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
(py31.venv)marca@marca-mac:~/dev/hg-repos/distlib$ python -c 'import distlib.compat; print(distlib.compat.match_hostname)'
<function match_hostname at 0x6103d8>
```