2014-04-22 ago avoid octal escape literals -- deprecated in scala-2.11.0;
2014-04-16 ago more specific support for sequence of words;
2014-02-18 ago tuned whitespace;
2014-02-18 ago tuned signature;
2012-08-29 ago clarified separated_chunks vs. space_explode;
2011-11-29 ago separate compilation of PIDE vs. Pure sources, which enables independent Scala library;
2011-11-28 ago explicit indication of modules for independent Scala library;
2011-11-28 ago separate module for concrete Isabelle markup;
2011-09-04 ago moved XML/YXML to src/Pure/PIDE;