XLIFF output: better "equiv-text" value for \n or \r content

Attached are a sample XML file and ITS rules to extract codes for the text \n and \r.

However, when extended code attributes are used, the equiv-text value for these codes is a literal newline/carriage return. Some users may prefer an alternate (visible) representation of these characters.

This issue also exists with XLIFF 2.0; I'll file a separate issue against the toolkit.