"Buildable" fixtures for the test-cases
Defined xdelta3.Stream type
Extension module renamed to _xdelta3
Defined _xdelta3.Source type
Changed convention of internal attribute names
Method _xdelta3.Source.set_curblk
Garbage collection for _xdelta3.Source
Refactored Source_set_curblk
Implemented _xdelta3.Stream.set_source