This changeset adds a unit test factory so that bookmark/link fixtures can be
created during tests.
Why are we writing tests for functionality that has been deprecated for years?
Because it's the Right Thing to Do.
See #18356.
git-svn-id: https://develop.svn.wordpress.org/trunk@37563 602fd350-edb4-49c9-b593-d223f7449a82
