- more direct native entry points.

- disallow bool as a return value for direct native calls because it only sets the lowest 8 bits of the return register.
- changed return type for several functions from bool to int where the return type was the only thing blocking use as direct native call.

src/p_things.cpp

@@ -552,13 +552,6 @@ PClassActor *P_GetSpawnableType(int spawnnum)
 	return NULL;
 }
 
-DEFINE_ACTION_FUNCTION(AActor, GetSpawnableType)
-{
-	PARAM_PROLOGUE;
-	PARAM_INT(num);
-	ACTION_RETURN_POINTER(P_GetSpawnableType(num));
-}
-
 struct MapinfoSpawnItem
 {
 	FName classname;	// DECORATE is read after MAPINFO so we do not have the actual classes available here yet.