* Check completeness of "junk" line handling.
  * Known issue: junk lines not processed inside "Comments" blocks. Need to add
    a parameter containing things-that-are-not-junk to parse_comments.
* Resync with spec
  * Handle \# in test descriptions, when the spec is updated for it
  * Spaces between # and directive, and directive and reason, should be optional
  * Clarify handling of unknown directives
* Comprehensive test suite.