The less than venerable `#alias_method_chain` has been deprecated in the latest version of Active Support. Fortunately, we only use it in two places. Replace with the longhand version using `alias_method` for forward compatibility. Not using Module#prepend in order to maintain compatibility with older versions of Ruby.
Fixes order-dependent test failures. Schema tests running after the original value was modified here would fail.
All test fixtures assume the presence of a root element, so make it the default. Fixes that tests expecting a root would fail unless `BaseTest`, which turns the setting on, ran first.
…alized instance variable