all: update light logs (and a few others) to the new model

core: reorg logs crashed, add a check for corner cases

build: fix xgo argument order when building from make

build: bundle the bootnode too into alltools

travis: support building mips32 and mips64 too

common/hexutil: implement TextMarshaler, TextUnmarshaler

* accounts, cmd, eth, ethdb: port logs over to new system

* ethdb: drop concept of cache distribution between dbs

* eth: fix some log nitpicks to make them nicer

Restricting encoding is silly.

This commit makes the wrapper types more generally applicable.
encoding.TextMarshaler is supported by most codec implementations (e.g.
for yaml).

The tests now ensure that package json actually recognizes the custom
marshaler implementation irrespective of how it is implemented.

The Uint type has new tests, too. These are tricky because uint size
depends on the CPU word size. Turns out that there was one incorrect
case where decoding returned ErrUint64Range instead of ErrUintRange.

All other functions return errors from package hexutil, ensure that
Decode does too.

This follows the change to common/math big integer parsing in PR #3699.

core/evm, core/vm: improved evm trace output

Added the ability to directly compile and run ethereum assembly using
the evm utility: `evm run <file>`. This is equivalant to `evm compile
<file> | evm run`.

* Improved the standard evm tracer output and renamed it to WriteTrace
which now takes an io.Writer to write the logs to.
* Added WriteLogs which writes logs to the given writer in a readable
format.
* evm utility now also prints logs generated during the execution.

The evm compile command implements a simple assembly language that compiles to
EVM bytecode.

errs: kill it with fire

Logger updates

* 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

core, eth: drop database block splitting upgrader

* Updated the list of go bootnodes: replaced BR with a new one, added US-WEST and AU.

* Updated bootnodes, minor go formatting change.

p2p, p2p/discover, p2p/nat: rework logging using context keys

common, eth/downloader, log: support terminal log formatting