2010-11-20 ago renamed raw "explode" function to "raw_explode" to emphasize its meaning;
2010-11-13 ago simplified message: malformed symbols are fully internalized, i.e. can be printed without crashing;
2010-11-13 ago eliminated slightly odd pervasive Symbol_Pos.symbol;
2010-11-13 ago simplified/robustified treatment of malformed symbols, which are now fully internalized (total Symbol.explode etc.);
2010-10-30 ago support for floating-point tokens in outer syntax (coinciding with inner syntax version);
2010-08-07 ago more robust treatment of Markup.token;
2010-08-07 ago simplified type XML.tree: embed Markup.T directly, avoid slightly odd triple;
2010-05-17 ago renamed structure OuterLex to Token and type token to Token.T, keeping legacy aliases for some time;