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/CollisionDispatch/SphereTriangleDetector.h

@@ -13,8 +13,8 @@ subject to the following restrictions:
 3. This notice may not be removed or altered from any source distribution.
 */
 
-#ifndef SPHERE_TRIANGLE_DETECTOR_H
-#define SPHERE_TRIANGLE_DETECTOR_H
+#ifndef BT_SPHERE_TRIANGLE_DETECTOR_H
+#define BT_SPHERE_TRIANGLE_DETECTOR_H
 
 #include "BulletCollision/NarrowPhaseCollision/btDiscreteCollisionDetectorInterface.h"
 
@@ -47,5 +47,5 @@ private:
 	btScalar	m_contactBreakingThreshold;
 	
 };
-#endif //SPHERE_TRIANGLE_DETECTOR_H
+#endif //BT_SPHERE_TRIANGLE_DETECTOR_H