src/Pure/Tools/doc.scala
2013-07-06 wenzelm 2013-07-06 quick access to release notes (imitating website/documentation.html);
2013-06-25 wenzelm 2013-06-25 clarified ISABELLE_DOC_FORMAT -- eliminated slightly odd fall-back;
2013-06-25 wenzelm 2013-06-25 slightly improved "isabelle doc" based on Isabelle/Scala; updated documentation of "isabelle display";