integrated named groups ("tok_type")

- switched from patt.exec to patt.xexec, but this loses the
  iterator aspekt (so you get the first match endlessly)
- switched to XRegExp.forEach to solve this
first working version with all groups

- <white> and <nl> might need further work
alternat. version using built-in RegExp

- about 7x faster than xregexp version
- about 15% faster than python version