This commit does a few things at once:

- Updates the tests to contain the latest data from ethereum/tests repo.
- Enables Constantinople state tests. This is needed to be able to
  fuzz-test the evm with constantinople rules.
- Fixes the error in opSAR that we've known about for some time. I was
  kind of saving it to see if we hit upon it with the random test
  generator, but it's difficult to both enable the tests and have the
  bug there -- we don't want to forget about it, so maybe it's better
  to just fix it.

params: fix golint warnings

* all: get rid of error when create mdb

* core: clean up variables definition

* all: inline mdb definition

The 'from' and 'to' methods on StateTransitions are reader methods and
shouldn't have inadvertent side effects on state.

It is safe to remove the check in 'from' because account existence is
implicitly checked by the nonce and balance checks. If the account has
non-zero balance or nonce, it must exist. Even if the sender account has
nonce zero at the start of the state transition or no balance, the nonce
is incremented before execution and the account will be created at that
time.

It is safe to remove the check in 'to' because the EVM creates the
account if necessary.

Fixes #15119

This commit reduces database I/O by not writing every state trie to disk.

Fixes #15777 because null is now allowed for hexutil.Bytes.

* core/types, core/vm, eth, tests: regenerate gencodec files

* Makefile: update devtools target

Install protoc-gen-go and print reminders about npm, solc and protoc.
Also switch to github.com/kevinburke/go-bindata because it's more
maintained.

* contracts/ens: update contracts and regenerate with solidity v0.4.19

The newer upstream version of the FIFSRegistrar contract doesn't set the
resolver anymore. The resolver is now deployed separately.

* contracts/release: regenerate with solidity v0.4.19

* contracts/chequebook: fix fallback and regenerate with solidity v0.4.19

The contract didn't have a fallback function, payments would be rejected
when compiled with newer solidity. References to 'mortal' and 'owned'
use the local file system so we can compile without network access.

* p2p/discv5: regenerate with recent stringer

* cmd/faucet: regenerate

* dashboard: regenerate

* eth/tracers: regenerate

* internal/jsre/deps: regenerate

* dashboard: avoid sed -i because it's not portable

* accounts/usbwallet/internal/trezor: fix go generate warnings

Also raise traceLimit once again and print the VM
error and output on failure.

* cmd, core, eth/tracers: support fancier js tracing

* eth, internal/web3ext: rework trace API, concurrency, chain tracing

* eth/tracers: add three more JavaScript tracers

* eth/tracers, vendor: swap ottovm to duktape for tracing

* core, eth, internal: finalize call tracer and needed extras

* eth, tests: prestate tracer, call test suite, rewinding

* vendor: fix windows builds for tracer js engine

* vendor: temporary duktape fix

* eth/tracers: fix up 4byte and evmdis tracer

* vendor: pull in latest duktape with my upstream fixes

* eth: fix some review comments

* eth: rename rewind to reexec to make it more obvious

* core/vm: terminate tracing using defers

* params: Updated finalized gascosts for ECMUL/MODEXP

* core,tests: Updates pending new tests

* tests: Updated with new tests

* core: revert state transition bugfix

* tests: Add expected failures due to  #15119

* cmd/evm: adds ability to run individual state test file

* cmd/evm: Fix statetest runner to be more json friendly

* cmd/evm, tests: minor polishes, dump state on fail

* core/vm: Make max_codesize only applicable post Spurious Dragon/158/155/161/170

* tests: Remove expected failure

Blockchain tests now include the "network" which determines the chain
config to use. Remove config matching based on test name and share the
name-to-config index with state tests.

Byzantium/Constantinople tests are still skipped because most of them
fail anyway.

Tests are now included as a submodule. This should make updating easier
and removes ~60MB of JSON data from the working copy.

State tests are replaced by General State Tests, which run the same test
with multiple fork configurations.

With the new test runner, consensus tests are run as subtests by walking
json files. Many hex issues have been fixed upstream since the last
update and most custom parsing code is replaced by existing JSON hex
types. Tests can now be marked as 'expected failures', ensuring that
fixes for those tests will trigger an update to test configuration. The
new test runner also supports parallel execution and the -short flag.

With this commit, core/state's access to the underlying key/value database is
mediated through an interface. Database errors are tracked in StateDB and
returned by CommitTo or the new Error method.

Motivation for this change: We can remove the light client's duplicated copy of
core/state. The light client now supports node iteration, so tracing and storage
enumeration can work with the light client (not implemented in this commit).

This commit adds pluggable consensus engines to go-ethereum. In short, it
introduces a generic consensus interface, and refactors the entire codebase to
use this interface.

* common/math: optimize PaddedBigBytes, use it more

name              old time/op    new time/op    delta
PaddedBigBytes-8    71.1ns ± 5%    46.1ns ± 1%  -35.15%  (p=0.000 n=20+19)

name              old alloc/op   new alloc/op   delta
PaddedBigBytes-8     48.0B ± 0%     32.0B ± 0%  -33.33%  (p=0.000 n=20+20)

* all: unify big.Int zero checks

Various checks were in use. This commit replaces them all with Int.Sign,
which is cheaper and less code.

eg templates:

    func before(x *big.Int) bool { return x.BitLen() == 0 }
    func after(x *big.Int) bool  { return x.Sign() == 0 }

    func before(x *big.Int) bool { return x.BitLen() > 0 }
    func after(x *big.Int) bool  { return x.Sign() != 0 }

    func before(x *big.Int) int { return x.Cmp(common.Big0) }
    func after(x *big.Int) int  { return x.Sign() }

* common/math, crypto/secp256k1: make ReadBits public in package math

Also tweak behaviour so colors are only enabled when stderr is a terminal.