Added Windows 8.1 to known OS types (as Windows81, Windows81_64)
Merge pull request #858 from mormegil-cz/add-win81-ostype

Added Windows 8.1 to known OS types (as Windows81, Windows81_64)
Merge branch 'master' of github.com:jedi4ever/veewee
Merge branch 'master' of github.com:nickchappell/veewee