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/BulletDynamics/Character/btCharacterControllerInterface.h

@@ -13,8 +13,8 @@ subject to the following restrictions:
 3. This notice may not be removed or altered from any source distribution.
 */
 
-#ifndef CHARACTER_CONTROLLER_INTERFACE_H
-#define CHARACTER_CONTROLLER_INTERFACE_H
+#ifndef BT_CHARACTER_CONTROLLER_INTERFACE_H
+#define BT_CHARACTER_CONTROLLER_INTERFACE_H
 
 #include "LinearMath/btVector3.h"
 #include "BulletDynamics/Dynamics/btActionInterface.h"
@@ -42,4 +42,5 @@ public:
 	virtual bool	onGround () const = 0;
 };
 
-#endif
+#endif //BT_CHARACTER_CONTROLLER_INTERFACE_H
+