Fixes for broadphase/paircache determinism.

Revert definition for ATTRIBUTE_ALIGNED16, and try to force sizeof(btSolverConstraint) by using unions with btScalar, for non-btScalar data types.
Use btAssert and not assert.
Don't access btAlignedObjectArray elements, for zero sets

src/BulletDynamics/Dynamics/btDiscreteDynamicsWorld.cpp

@@ -712,7 +712,7 @@ void	btDiscreteDynamicsWorld::solveConstraints(btContactSolverInfo& solverInfo)
 		sortedConstraints[i] = m_constraints[i];
 	}
 
-//	assert(0);
+//	btAssert(0);