It turns out we forgot to add support for internal catalog munging clauses
to SQLite support. The catalogs being normalized means there's no extra work
here other than allowing the parser to accept those clauses and then pass
them over to our generic `copy-database' method implementation.
It is to be noted that SQLite has no support for schemas as per the standard
and PostgreSQL, so that when we inspect the database schema we create a nil
entry here. It's then not possible to ALTER SCHEMA nil RENAME TO 'target';
unfortunately, but it's easy enough to SET search_path to 'target' anyway,
as shown in the modified test case.
Fix#552.