Make it possible to disable filtering for a pattern.
Rationale: Apparently there were no way to disable for example win32text extension locally.
RFC: Can it already be done another way?
adding a
abort: username 'foo\nbar1' contains a newline
abort: username 'foo\nbar2' contains a newline
transaction abort!
rollback completed
abort: username 'foo\nbar3' contains a newline!