Update to box2d 2.4.1

src/libraries/box2d/b2_time_step.h

@@ -22,10 +22,11 @@
 #ifndef B2_TIME_STEP_H
 #define B2_TIME_STEP_H
 
+#include "b2_api.h"
 #include "b2_math.h"
 
 /// Profiling data. Times are in milliseconds.
-struct b2Profile
+struct B2_API b2Profile
 {
 	float step;
 	float collide;
@@ -38,7 +39,7 @@ struct b2Profile
 };
 
 /// This is an internal structure.
-struct b2TimeStep
+struct B2_API b2TimeStep
 {
 	float dt;			// time step
 	float inv_dt;		// inverse time step (0 if dt == 0).
@@ -49,21 +50,21 @@ struct b2TimeStep
 };
 
 /// This is an internal structure.
-struct b2Position
+struct B2_API b2Position
 {
 	b2Vec2 c;
 	float a;
 };
 
 /// This is an internal structure.
-struct b2Velocity
+struct B2_API b2Velocity
 {
 	b2Vec2 v;
 	float w;
 };
 
 /// Solver Data
-struct b2SolverData
+struct B2_API b2SolverData
 {
 	b2TimeStep step;
 	b2Position* positions;