Create needed directories on the fly.
A generated source may be a whole directory of source files.
Ahven needs a directory for test results.  Ahven needs to know which kind of operating system we're running the tests on.
More precise ignore patterns. - So we can see the /tests/ahven/ directory.
First small Ahven based test of Black.Text_IO.
Proper writing of Stream_Element_Vectors to a stream.
Implemented testing of Text_IO.New_Line and Text_IO.Put_Line.