Changes both major and minor:

[sydb]

• Major: Use a pattern prefix on RELAX NG patterns (and references to them).
• Add a colophonic comment block at the top with some metadata.
• Minor: Use atomic comparison operators when neither L nor R is a sequence.
• Minor: Do not bother with 2nd argument to tokenize().
• Minor: Remove some tests for error conditions that should be caught before this point in processing (by the PLODD schema).
• Minor: Changes to comments and documentation.