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/NarrowPhaseCollision/btSimplexSolverInterface.h

@@ -15,8 +15,8 @@ subject to the following restrictions:
 
 
 
-#ifndef SIMPLEX_SOLVER_INTERFACE_H
-#define SIMPLEX_SOLVER_INTERFACE_H
+#ifndef BT_SIMPLEX_SOLVER_INTERFACE_H
+#define BT_SIMPLEX_SOLVER_INTERFACE_H
 
 #include "LinearMath/btVector3.h"
 
@@ -59,5 +59,5 @@ class btSimplexSolverInterface
 
 };
 #endif
-#endif //SIMPLEX_SOLVER_INTERFACE_H
+#endif //BT_SIMPLEX_SOLVER_INTERFACE_H