Update to box2d 2.4.1

src/libraries/box2d/b2_stack_allocator.h

@@ -23,12 +23,13 @@
 #ifndef B2_STACK_ALLOCATOR_H
 #define B2_STACK_ALLOCATOR_H
 
+#include "b2_api.h"
 #include "b2_settings.h"
 
 const int32 b2_stackSize = 100 * 1024;	// 100k
 const int32 b2_maxStackEntries = 32;
 
-struct b2StackEntry
+struct B2_API b2StackEntry
 {
 	char* data;
 	int32 size;
@@ -38,7 +39,7 @@ struct b2StackEntry
 // This is a stack allocator used for fast per step allocations.
 // You must nest allocate/free pairs. The code will assert
 // if you try to interleave multiple allocate/free pairs.
-class b2StackAllocator
+class B2_API b2StackAllocator
 {
 public:
 	b2StackAllocator();