Unnecessary deallocation?

Hi there,

```
template <typename T> struct fifo_manip<T, false, true>     { static void access (T && slot, T&& arg)  { arg = T(); std::swap (slot, arg); } };
```

shouldn't this simply be:

```
template <typename T> struct fifo_manip<T, false, true>     { static void access (T && slot, T&& arg)  { std::swap (slot, arg); } };
```

Or, what is the purpose of `arg = T()`?
