This adds a lexer capable of handling the XDR protocol files.
The lexical rquirements are detailed in
https://www.rfc-editor.org/rfc/rfc4506#section-6.2
pytest is introduced as a build dependancy for testing python
code.
Reviewed-by: Michal Privoznik <mprivozn@redhat.com>
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
