Ah, it turns out NetrekXP does not use SDL, guess it branched off before
that was added.  Since sound mixing would be a really good thing, I'm
going to look into putting it into NetrekXP following what was done to the
COW client.  I looked over the Changelog for COW, it seemed SDL was one of
the larger changes.  Any other things that were added within the last 6
years that might be worth porting over to XP?