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/btScaledBvhTriangleMeshShape.h

@@ -13,8 +13,8 @@ subject to the following restrictions:
 3. This notice may not be removed or altered from any source distribution.
 */
 
-#ifndef SCALED_BVH_TRIANGLE_MESH_SHAPE_H
-#define SCALED_BVH_TRIANGLE_MESH_SHAPE_H
+#ifndef BT_SCALED_BVH_TRIANGLE_MESH_SHAPE_H
+#define BT_SCALED_BVH_TRIANGLE_MESH_SHAPE_H
 
 #include "BulletCollision/CollisionShapes/btBvhTriangleMeshShape.h"
 
@@ -90,4 +90,4 @@ SIMD_FORCE_INLINE	const char*	btScaledBvhTriangleMeshShape::serialize(void* data
 }
 
 
-#endif //BVH_TRIANGLE_MESH_SHAPE_H
+#endif //BT_SCALED_BVH_TRIANGLE_MESH_SHAPE_H