Replace all hardcoded 1e30(f) by BT_LARGE_FLOAT, defined in btScalar.h as 1e18(f) so that its square still fits in FLT_MAX

Thanks to Ole K. for reporting! http://code.google.com/p/bullet/issues/detail?id=206

src/BulletCollision/CollisionDispatch/SphereTriangleDetector.cpp

@@ -37,7 +37,7 @@ void	SphereTriangleDetector::getClosestPoints(const ClosestPointInput& input,Res
 	btVector3 point,normal;
 	btScalar timeOfImpact = btScalar(1.);
 	btScalar depth = btScalar(0.);
-//	output.m_distance = btScalar(1e30);
+//	output.m_distance = btScalar(BT_LARGE_FLOAT);
 	//move sphere into triangle space
 	btTransform	sphereInTr = transformB.inverseTimes(transformA);