Add OpenTyrian package (SDL game)

[Peter: hide -data package if opentyrian isn't enabled]
Signed-off-by: Julien Boibessot <julien.boibessot@armadeus.com>
Acked-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>