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/LinearMath/btTransform.h

@@ -14,8 +14,8 @@ subject to the following restrictions:
 
 
 
-#ifndef btTransform_H
-#define btTransform_H
+#ifndef BT_TRANSFORM_H
+#define BT_TRANSFORM_H
 
 
 #include "btMatrix3x3.h"
@@ -298,7 +298,7 @@ SIMD_FORCE_INLINE	void	btTransform::deSerializeDouble(const btTransformDoubleDat
 }
 
 
-#endif
+#endif //BT_TRANSFORM_H