Correct stack size validation for MUL, CALLDATACOPY, EXTCODESIZE, BLOCKH...

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* Implemented `eth_logs`
* Fixed issue with `filter.Find()` where logs were appended to an
  incorrect, non-returned slice resulting in no logs found

Don't print per-function testing results

Fix failing tests and speed up Travis builds

This should yield another 30-second speed up. Nobody looks
at the output of those anyway. We might want bring back gofmt later
and actually fail the build if source is not formatted.

This should decrease test runtime to about 30 seconds.