SpawnTurret( <classname>, <origin>, <weaponinfoname> )
Module: Spawn
Summary:
Spawns a new turret, eg MG42 or flak gun and returns a reference to it
Required Args:
1 : <classname> The classname of the entity (constant string)
2 : <origin> The position of the vehicle (vector)
3 : <weaponinfoname> The name of the weapon info to use for this turret (string)