doc.tcl

- Accomplished major rewrite and cleanup of the comment block parser. The revised design allows us to express parsing states (context, description, part) as well as their substates reflecting the comment line processed (tag, text, space) directly. The design follows a METHODS-FOR-STATES strategy. Also, the parsing logic is now self-contained and is not interwoven with the class hierarchy documentation entities anymore (i.e., the former process() method of Entity and its subclasses). - The modal/reactive design of the comment block parser has been streamlined: There is a CommentBlockParser class which acts as the event source. The actual parsing is achieved by the mixin-refined entity objects by reacting upon the parsing events (process, parse, next). - Adjusted the tests in doc.tcl accordingly. - Changed occurrences of [info callable] to reflect the latest changes.