Gl next query

To get the discussion going about gl query objects.

(Previously named QueryTimeElapsed, I renamed it to QueryTimeSwapped here in order to make the swapping mechanism more explicit.)
Curious (though I don't have a branch set up right now to test), does this cause a warnings when used to index the array?  It seems to me an equal and less verbose solution could be done with `size_t`, which is what `std::array` wants anyway:

```cpp
size_t mSwapIndex;
...
mSwapIndex = 1 - mSwapIndex;
```