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

src/scenedit/scen.keydlgs.cpp

@@ -246,7 +246,7 @@ short choose_text(eStrType list, unsigned short cur_choice, cDialog* parent, con
 			}
 			break;
 		case STRT_RACE:
-			for(int i = 0; i < 20; i++) {
+			for(int i = 0; i < 22; i++) {
 				strings.push_back(get_str("traits", i * 2 + 33));
 			}
 			break;