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/Gimpact/btGImpactCollisionAlgorithm.h

@@ -21,8 +21,8 @@ subject to the following restrictions:
 3. This notice may not be removed or altered from any source distribution.
 */
 
-#ifndef BVH_CONCAVE_COLLISION_ALGORITHM_H
-#define BVH_CONCAVE_COLLISION_ALGORITHM_H
+#ifndef BT_GIMPACT_BVH_CONCAVE_COLLISION_ALGORITHM_H
+#define BT_GIMPACT_BVH_CONCAVE_COLLISION_ALGORITHM_H
 
 #include "BulletCollision/CollisionDispatch/btActivatingCollisionAlgorithm.h"
 #include "BulletCollision/BroadphaseCollision/btDispatcher.h"
@@ -303,4 +303,4 @@ public:
 
 
 
-#endif //BVH_CONCAVE_COLLISION_ALGORITHM_H
+#endif //BT_GIMPACT_BVH_CONCAVE_COLLISION_ALGORITHM_H

src/BulletCollision/Gimpact/btQuantization.h

@@ -1,5 +1,5 @@
-#ifndef BT_QUANTIZATION_H_INCLUDED
-#define BT_QUANTIZATION_H_INCLUDED
+#ifndef BT_GIMPACT_QUANTIZATION_H_INCLUDED
+#define BT_GIMPACT_QUANTIZATION_H_INCLUDED
 
 /*! \file btQuantization.h
 *\author Francisco Leon Najera
@@ -85,4 +85,4 @@ SIMD_FORCE_INLINE btVector3 bt_unquantize(
 
 
 
-#endif // GIM_VECTOR_H_INCLUDED
+#endif // BT_GIMPACT_QUANTIZATION_H_INCLUDED

src/BulletCollision/Gimpact/btTriangleShapeEx.h

@@ -22,8 +22,8 @@ subject to the following restrictions:
 */
 
 
-#ifndef TRIANGLE_SHAPE_EX_H
-#define TRIANGLE_SHAPE_EX_H
+#ifndef GIMPACT_TRIANGLE_SHAPE_EX_H
+#define GIMPACT_TRIANGLE_SHAPE_EX_H
 
 #include "BulletCollision/CollisionShapes/btCollisionShape.h"
 #include "BulletCollision/CollisionShapes/btTriangleShape.h"
@@ -177,4 +177,4 @@ public:
 };
 
 
-#endif //TRIANGLE_MESH_SHAPE_H
+#endif //GIMPACT_TRIANGLE_MESH_SHAPE_H