* fix modexp bug: return 0 if base=0 (#6424)
* Running state test using parity-evm (#6355)
* Initial version of state tests.
* Refactor state to support tracing.
* Unify TransactResult.
* Add test.
* Byzantium updates
This is a huge change, which includes some changes to replace code that
originally cloned to reuse allocations instead. The updated
`elastic-array` crate renames its consuming `Vec`-conversion method to
`into_vec`, which means that I can do a simple
`sed -i 's/to_vec/into_vec/'` and then fix the compilation errors.
This commit is probably a minor performance win and definitely a
significant readability win.
* state backend trait mirroring state_db API
* minimal state backend trait
make state module public
* fix json tests
* return errors on database corruption
* fix tests, json tests
* fix remainder of build
* add Backend bound on state
* The front-end for each hard-fork, also EIP-160.
* Address EIP161 a/c
* Include EIP-161b
* EIP-161 part d.
* Fix test build.
* Fix one test, add another.
* Fix use of bloom & renaming.
* Initial groundwork for EIP-155
* Fix minor bug.
* Fix all tests finally.
* Rest of EIP-155.
* Add tests for EIP-155 algorithm.
Update transaction tests validation.
* Minor reformat.
* Address grumbles.
* Remove unused code.
* Fix SUICIDE gas mechanism and add consensus tests.
* Remove commented code.
* Set Frontier hardfork block number
* Fix warning.
* Transaction tests,
* Actually enable fat db, and do RPCs for it.
* Implement HashDB traits for AccountDB.
* user defaults
* finished user defaults
* user defaults are network-dependent
* added tests for newly added functions, logger is initialized first
* dir cleanup in progress
* user_file is placed next to snapshots
* fixing requested change
