Allow using wxZlib{Input,Output}Stream too, meaning that the sample can
now also work with .gz files, handling them as a degenerate (because
containing only a single file) special case of archives.
The changes here -- which should be viewed ignoring whitespace to be
actually readable -- don't modify the existing code and just add the
possibility to use a wxFilterClassFactory if there is no
wxArchiveClassFactory corresponding to the specified file extension.
This sample shows usage of wxArchiveStream and wxArchiveFactory.
It also allows for easy testing of wxArchiveStream implementations
outside of the unit tests.
See https://github.com/wxWidgets/wxWidgets/pull/730