Add EXCHANGE test for EOF

[jochem-brouwer]

There is an exchange test in the latest EOF test releases, which we pass. However, our current implementation treats our stack in reverse (in case of a stack of 1024 items, it would still try to exchange items super deep into the stack instead of at the top).

EVMONE has this EOF test:

0xef000101000402000100120400000000800004600160026003e80060005560015560025500

It simply calls EXCHANGE[0], which thus means to exchange the item 1 position below the top with the item 2 positions below the top.

EthereumJS does not pass this test, which it clearly should. So apparently the current EXCHANGE test also works on reversed arrays (so if you would reverse the stack, so read either from the top or from the bottom) then it would still pass.