Yoichi Hirai bb6115b737 vm, ethapi: add limit option to traceTransaction
that specifies the maximum number of elements in the `structLogs`
output.  This option is useful for debugging a transaction that
involves a large number of repetition.

For example,
```
debug.traceTransaction(tx, {disableStorage: true, limit: 2})
```
shows at most the first two steps in the `structLogs`.
2016-09-30 17:36:00 +02:00
..
2016-06-22 13:42:39 +02:00