generalize ensure_sort_datatype to ensure_sort in quickcheck_common to allow generators for abstract types;
adding common datatype interpretation to quickcheck_common;
Notes on Cygwin
===============
* http://www.cygwin.com/
* http://www.cygwin.com/cygwin-ug-net/ntsec.html
* http://chinese-watercolor.com/LRP/printsrv/cygwin-sshd.html