The white list is done by setting a metatable on the global table before initializing
any library. The metatable set the `__newindex` field to a function that check
the white list before adding the field to the table. Fields which is not on the
white list are simply ignored.
After initialization phase is done we protect the global table and each table
that might be reachable from the global table. For each table we also protect
the table metatable if exists.
