Update to box2d 2.4.1

src/libraries/box2d/b2_block_allocator.h

@@ -23,7 +23,8 @@
 #ifndef B2_BLOCK_ALLOCATOR_H
 #define B2_BLOCK_ALLOCATOR_H
 
-#include "box2d/b2_settings.h"
+#include "b2_api.h"
+#include "b2_settings.h"
 
 const int32 b2_blockSizeCount = 14;
 
@@ -33,7 +34,7 @@ struct b2Chunk;
 /// This is a small object allocator used for allocating small
 /// objects that persist for more than one time step.
 /// See: http://www.codeproject.com/useritems/Small_Block_Allocator.asp
-class b2BlockAllocator
+class B2_API b2BlockAllocator
 {
 public:
 	b2BlockAllocator();