2005-10-04 ago minor tweaks for Poplog/ML;
2005-09-15 ago TableFun/Symtab: curried lookup and update;
2005-09-13 ago replaced DATA_FAIL by EXCEPTION;
2005-09-01 ago curried_lookup/update;
2005-08-16 ago type proof: theory_ref instead of theory (make proof contexts independent entities);
2005-07-19 ago Inttab.defined;
2005-07-06 ago check_thy: less invocations, less verbose;
2005-06-29 ago added joinable;
2005-06-22 ago begin_thy: merge maximal imports;
2005-06-20 ago improved treatment of intermediate checkpoints: actual copy
2005-06-17 ago added type theory: generic theory contexts with unique identity,
2005-04-21 ago superceded by Pure.thy and CPure.thy;
2005-02-13 ago Deleted Library.option type.
2004-06-21 ago Merged in license change from Isabelle2004
2004-06-20 ago use_output: Symbol.escape;
2001-10-17 ago tuned comments;
2001-01-16 ago use_output: proper handling of non-ASCII symbols;
2001-01-16 ago use_text etc.: proper output of error messages;
2001-01-12 ago use_mltext: priority output;
2000-08-14 ago use_let: exclude 'val';
2000-05-05 ago tuned msg;
2000-03-06 ago added use_mltext, use_mltext_theory, use_let, use_setup (from isar_thy.ML);
1999-03-09 ago tuned;
1999-02-08 ago added fetch, fetch_theory;
1999-02-05 ago setmp: theory option;
1999-02-03 ago Global theory context (used to be in Thy/context.ML);