Add two new monster races to account for previously-hardcoded special cases

- Skeletal undead are distinguished from normal undead in that they leave sfx bones when they die; normal undead leave no sfx. In all other respects, they are the same.
- Goblins are distinguished from other humanoids in their death sound. In all other respects, they are the same.
- The sleep() function for players now checks for racial immunity - eg undead, plants, etc
- Protect form humanoids now also protects from sliths, nephilim, vahnatai, and goblins, as it should (this is legacy behaviour)
- Protect from undead still also protects from skeletal undead
- The special case for the ogre death sound is removed; that might mean that ogres can now have a femal death sound? I'm not quite sure what the purpose of the exception was.
- The if species node can now check for non-standard races in the party
- When loading a legacy scenario, it attempts to detect skeletal undead and goblins by the presence of the words "Skeleton" and "Goblin" in the name, respectively

rsrc/strings/traits.txt

@@ -69,3 +69,7 @@ Magical
 Plant
 
 Bird
+
+Skeletal Undead
+
+Goblin