interhg: allow more flexible pattern specification (fixes 2/3 of
issue699)
- something else than "pat" followed by a number can be used as key
- something else than "/" can be used as delimiter
- "ilmsux" flags (e.g. "i" for case insensitive) can be used
Don't decode unicode strings.
This does not work with python2.3 and is probably not useful anyway with 2.4.