* rpc: send websocket ping when connection is idle

* rpc: use non-blocking send for websocket pingReset

This moves all v4 protocol definitions to a new package, p2p/discover/v4wire.
The new package will be used for low-level protocol tests.

* core/vm: implement EIP 2315, subroutines for the EVM

* core/vm: eip 2315 - lintfix + check jump dest validity + check ret stack size constraints

  logger: markdown-friendly traces, validate jumpdest, more testcase, correct opcodes

* core/vm: update subroutines acc to eip: disallow walk-into

* core/vm/eips: gas cost changes for subroutines

* core/vm: update opcodes for EIP-2315

* core/vm: define RETURNSUB as a 'jumping' operation + review concerns
Co-authored-by: Martin Holst Swende <martin@swende.se>

* replace gosigar with gopsutil

* removed check for whether GOOS is openbsd

* removed accidental import of runtime

* potential fix for difference in units between gosig and gopsutil

* fixed lint error

* remove multiplication factor

* uses cpu.ClocksPerSec as the multiplication factor

* changed dependency from shirou to renaynay (#20)

* updated dep

* switching back from using renaynay fork to using upstream as PRs were merged on upstream

* removed empty line

* optimized imports

* tidied go mod

This PR makes use of go 1.13 error handling, wrapping errors and using
errors.Is to check a wrapped root-cause. It also removes the travis
builders for go 1.11 and go 1.12.

* trie: add hasRightElement indicator

* trie: ensure the range is monotonic increasing

* trie: address comment and fix lint

* trie: address comment

* trie: make linter happy
Co-authored-by: Péter Szilágyi <peterke@gmail.com>

Co-authored-by: linjing <linjingjing@baidu.com>

This adds a new API method on core.BlockChain to allow interrupting
running data inserts, and calls the method before shutting down the
downloader.

The BlockChain interrupt checks are now done through a method instead
of inlining the atomic load everywhere. There is no loss of efficiency from
this and it makes the interrupt protocol a lot clearer because the check is
defined next to the method that sets the flag.

* build: upgrade to golangci-lint v1.27.0

* build: raise lint timeout to 3 minutes

* trie: fix for range proof

* trie: fix typo

* ethstats: avoid blocking chan when received invalid stats request

* ethstats: minor code polishes
Co-authored-by: Péter Szilágyi <peterke@gmail.com>

* metrics/prometheus: define type once for histograms

* metrics/prometheus: test collector

This PR reimplements the light client server pool. It is also a first step
to move certain logic into a new lespay package. This package will contain
the implementation of the lespay token sale functions, the token buying and
selling logic and other components related to peer selection/prioritization
and service quality evaluation. Over the long term this package will be
reusable for incentivizing future protocols.

Since the LES peer logic is now based on enode.Iterator, it can now use
DNS-based fallback discovery to find servers.

This document describes the function of the new components:
https://gist.github.com/zsfelfoldi/3c7ace895234b7b345ab4f71dab102d4

* trie: implement range proof with non-existent edge proof

* trie: fix cornercase

* trie: consider empty range

* trie: add singleSide test

* trie: support all-elements range proof

* trie: fix typo

* trie: tiny typos and formulations
Co-authored-by: Péter Szilágyi <peterke@gmail.com>

* abi/bind/backends: testcase for double-lock

* accounts: add blockByNumberNoLock to avoid double-lock

* backend/simulated: use stateroot, not blockhash for retrieveing state
Co-authored-by: Martin Holst Swende <martin@swende.se>

* cmd/clef, signer/core: use better terminal input for passwords, make it possible to avoid boot-up warning

* all: move commonly used prompter to isolated (small) package

* cmd/clef: Add new --acceptWarn to clef README

* cmd/clef: rename flag 'acceptWarn' to 'suppress-bootwarn'
Co-authored-by: ligi <ligi@ligi.de>

* accounts/abi: simplified reflection logic

* accounts/abi: simplified reflection logic

* accounts/abi: removed unpack

* accounts/abi: removed comments

* accounts/abi: removed uneccessary complications

* accounts/abi: minor changes in error messages

* accounts/abi: removed unnused code

* accounts/abi: fixed indexed argument unpacking

* accounts/abi: removed superfluous test cases

This commit removes two test cases. The first one is trivially invalid as we have the same
test cases as passing in packing_test.go L375. The second one passes now,
because we don't need the mapArgNamesToStructFields in unpack_atomic anymore.
Checking for purely underscored arg names generally should not be something we do
as the abi/contract is generally out of the control of the user.

* accounts/abi: removed comments, debug println

* accounts/abi: added commented out code

* accounts/abi: addressed comments

* accounts/abi: remove unnecessary dst.CanSet check

* accounts/abi: added dst.CanSet checks

Co-authored-by: Hao Duan <duan.hao@hyperchain.cn>

* core: fix missing receipt

* core: address comment

* accounts/abi: allow overloaded argument names

In solidity it is possible to create the following contract:
```
contract Overloader {
    struct F { uint _f; uint __f; uint f; }
    function f(F memory f) public {}
}
```
This however resulted in a panic in the abi package.

* accounts/abi fixed error handling

* accounts/abi/bind: added test cases for waitDeployed

* accounts/abi/bind: added test case for boundContract

* accounts/abi/bind: removed unnecessary resolve methods

* accounts/abi: moved topics from /bind to /abi

* accounts/abi/bind: cleaned up format... functions

* accounts/abi: improved log message

* accounts/abi: added type tests

* accounts/abi/bind: remove superfluous template methods

* cmd, miner: add noempty-precommit flag

* cmd, miner: get rid of external flag

* miner: change bool to atomic int

* miner: fix tiny typo
Co-authored-by: Péter Szilágyi <peterke@gmail.com>

* core/rawdb : log format fix for Unindexing transaction

* core/rawdb: tiny fixup
Co-authored-by: Péter Szilágyi <peterke@gmail.com>

* les: drop the message if the entire p2p connection is stuck

* les: fix lint

core: fixup blockchain tests

params: bump CHTs for the v1.9.14 release