Fix the way URL parameters are encoded

I'm not sure on the intended functionality here but it seems to be broken to me.

running:

`$this->createUrl('checkout/confirmation', array('order'=> array('666', '999')));`

Gives me

`/checkout/confirmation/order%5B0%5D/666/order%5B1%5D/999`
But it should give:
`/checkout/confirmation/order[0]/666/order[1]/999`

Again, I'm not sure if this was intended, although I can't see why it would be, but I can't seem to find any bug reports or other people having issues with it.