2010-04-08 ago added imperative SAT checker; improved headers of example files; adopted IsaMakefile
2010-02-08 ago avoid upto in generated code (is infix operator in library.ML)
2009-10-17 ago eliminated hard tabulators, guessing at each author's individual tab-width;
2009-06-30 ago restored
2009-06-30 ago temporary workaround
2009-03-23 ago moved Imperative_HOL examples to Imperative_HOL/ex