||Untamed: To be replaced with a lexer based on Antlr.
||Untamed: A FileFeeder reads its input from a Reader which it assumes starts at the
beginning of line 1 in the text unit (file?) described by the Url.
||Untamed: Keeps track of indentation info for BaseLexer's subclasses and clients.
||Untamed: The large number of bogus messages in this class is a symptom of a need to
||Untamed: For feeding in one line of Twine at a time taken from a dynamically
provided Twine source.
||Safe: This class provides some conveniences for manipulating E URI-tokens.