QUEEN: Switch all savegame usage back to "queen.sXX" format.

The target is not just a bare "queen", but is postfixed by language
variant (and CD if used) etc.

Using this for the savegame naming is good as it allows several language
variants to have different co-existing savegame sets without causing
conflicts.

Currently the queen engine uses a single set of savegames named in the
format "queen.sXX" which are used for all languages. This should be
migrated from in future.