Fix DistanceJoint type information

src/modules/physics/box2d/DistanceJoint.cpp

@@ -32,6 +32,8 @@ namespace physics
 namespace box2d
 {
 
+love::Type DistanceJoint::type("DistanceJoint", &Joint::type);
+
 DistanceJoint::DistanceJoint(Body *body1, Body *body2, float x1, float y1, float x2, float y2, bool collideConnected)
 	: Joint(body1, body2)
 	, joint(NULL)

src/modules/physics/box2d/DistanceJoint.h

@@ -39,6 +39,8 @@ class DistanceJoint : public Joint
 {
 public:
 
+	static love::Type type;
+
 	/**
 	 * Creates a DistanceJoint connecting body1 to body2.
 	 **/