Fixes <http://webkit.org/b/72609> Lion Leaks bot complains about a bunch of leaks that
aren't WebKit's fault

Reviewed by Antti Koivisto.

* Scripts/old-run-webkit-tests:
(countAndPrintLeaks):
* Scripts/webkitpy/layout_tests/port/leakdetector.py:
(LeakDetector._callstacks_to_exclude_from_leaks):
Added some call stacks to exclude on Lion that represent leaks in lower-level frameworks.

* Scripts/webkitpy/layout_tests/port/mac.py:
(MacPort.is_lion): Added.

* Scripts/webkitpy/layout_tests/port/mac_unittest.py:
(MacPortTest.test_is_version_methods): Added tests for the is_leopard/is_snowleopard/is_lion
methods.

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@100618 268f45cc-cd09-0410-ab3c-d52691b4dbfc