eth/downloader: port over old logs from glog to log15

vendor: update HID library for glibc < v2.17 build

* common: remove CurrencyToString

Move denomination values to params instead.

* common: delete dead code

* common: move big integer operations to common/math

This commit consolidates all big integer operations into common/math and
adds tests and documentation.

There should be no change in semantics for BigPow, BigMin, BigMax, S256,
U256, Exp and their behaviour is now locked in by tests.

The BigD, BytesToBig and Bytes2Big functions don't provide additional
value, all uses are replaced by new(big.Int).SetBytes().

BigToBytes is now called PaddedBigBytes, its minimum output size
parameter is now specified as the number of bytes instead of bits. The
single use of this function is in the EVM's MSTORE instruction.

Big and String2Big are replaced by ParseBig, which is slightly stricter.
It previously accepted leading zeros for hexadecimal inputs but treated
decimal inputs as octal if a leading zero digit was present.

ParseUint64 is used in places where String2Big was used to decode a
uint64.

The new functions MustParseBig and MustParseUint64 are now used in many
places where parsing errors were previously ignored.

* common: delete unused big integer variables

* accounts/abi: replace uses of BytesToBig with use of encoding/binary

* common: remove BytesToBig

* common: remove Bytes2Big

* common: remove BigTrue

* cmd/utils: add BigFlag and use it for error-checked integer flags

While here, remove environment variable processing for DirectoryFlag
because we don't use it.

* core: add missing error checks in genesis block parser

* common: remove String2Big

* cmd/evm: use utils.BigFlag

* common/math: check for 256 bit overflow in ParseBig

This is supposed to prevent silent overflow/truncation of values in the
genesis block JSON. Without this check, a genesis block that set a
balance larger than 256 bits would lead to weird behaviour in the VM.

* cmd/utils: fixup import

Drop legacy commands

This command was meant as a hackish way to upgrade our chain database way back
when nobody cared for live updates and the size of the database along with its
import times was small. With the current database weighing hundreds of GBs and
processing times of many days, this command is just ludicrous.

All the state and block tests are ran as part of our CU builds internally, as
well as have been added to hive black-box tests. As such, there is no reason for
maintaining an extra standalone tool.

Only ethereum/rpc-tests used this command, which hasn't been maintained for over
a year now, a lot of tests failing. What's left of it was moved underneath hive,
which can run the entire test against a black-box geth without special commands.

Also a new RPC test suite is being added which is also based on black box tests,
not needing special commands any more.

Contextual logger

* whisper: wnode updated for tests with geth

* whisper: updated processing of incoming messages

* whisper: symmetric encryption updated

* whisper: filter id type changed to enhance security

* whisper: allow filter without topic for asymmetric encryption

* whisper: POW updated

* whisper: logging updated

* whisper: spellchecker update

* whisper: error handling changed

* whisper: JSON field names fixed

This PR implements a differenceIterator, which allows iterating over trie nodes
that exist in one trie but not in another. This is a prerequisite for most GC
strategies, in order to find obsolete nodes.

Removed exported statedb object accessors, reducing the chance for nasty
bugs to creep in. It's also ugly and unnecessary to have these methods.

travis: only run go vet and misspell on latest Go

travis, appveyor: update builders to Go 1.8

* cmd/geth: added 'geth bug' command

Added bug command to geth, which will open a browser window
with an issue template and some additional system information.

* cmd/geth: update bug with better infos

* cmd/geth: added browser fallback

* cmd/geth: govet yo momma

accounts/usbwallet: swap karalabe/gousb to karalabe/hid