add the BT_ prefix for all #ifdef guards, to avoid conflicts with developers own header defines.

Fixes Issue 497

//license header
#ifndef BT_RIGIDBODY_H
#define BT_RIGIDBODY_H
class btRigidBody
{
};
#endif //BT_RIGIDBODY_H

src/BulletCollision/CollisionShapes/btBoxShape.h

@@ -13,8 +13,8 @@ subject to the following restrictions:
 3. This notice may not be removed or altered from any source distribution.
 */
 
-#ifndef OBB_BOX_MINKOWSKI_H
-#define OBB_BOX_MINKOWSKI_H
+#ifndef BT_OBB_BOX_MINKOWSKI_H
+#define BT_OBB_BOX_MINKOWSKI_H
 
 #include "btPolyhedralConvexShape.h"
 #include "btCollisionMargin.h"
@@ -313,6 +313,6 @@ public:
 };
 
 
-#endif //OBB_BOX_MINKOWSKI_H
+#endif //BT_OBB_BOX_MINKOWSKI_H