Build type information on first use (load-time), instead of using a hardcoded list

--HG--
branch : dynamiccore2

src/modules/physics/box2d/PulleyJoint.cpp

@@ -32,6 +32,8 @@ namespace physics
 namespace box2d
 {
 
+love::Type PulleyJoint::type(&Joint::type);
+
 PulleyJoint::PulleyJoint(Body *bodyA, Body *bodyB, b2Vec2 groundAnchorA, b2Vec2 groundAnchorB, b2Vec2 anchorA, b2Vec2 anchorB, float ratio, bool collideConnected)
 	: Joint(bodyA, bodyB)
 	, joint(NULL)