Text Handling

- Migrated the splitq implementation over to the Lexer. Now it handles all
  Unicode spaces.  Jsut need to obsolete the old version.
Lexer

- Implemented Lexer::word, which is just like ::token, but does not
  understand dates, durations or operators.
- Implemented Lexer::split, which uses Lexer::word.
- Added unit tests.
Text

- Removed splitq function and tests, migrated code over to the new
  Lexer::split.