p2p/nat: fix a bytes based net.IP comparison

p2p/discover, p2p/discv5: use flexible comparison for IPs

core: import future blocks one-by-one, enfore chain ancestry

VERSION, params: start Geth 1.5.6 development cycle

params: stable version 1.5.5

miner: clean up unconfirmed mined block tracking

cmd/swarm: one command  with subcommands

build: Ubuntu wily was officially deprecated, drop support

core: init pending state in tx pool on creation

cmd/utils, eth: Add gzip support for chain dump and restore

travis, appveyor: build with Go 1.7.4

cmd/geth: drop legacy android code

Miner race fixes

cmd/swarm: subsume cmd/bzz* under cmd/swarm as subcommands

les, p2p/discv5: implement server pool, improve peer selection, light fetcher and topic searching

netstats: time and block history

NSIS has a default MAX_STR_LEN of 1024. If $ENV{PATH} is longer
the returned string is truncated to an empty string. Its then not
possible to distinguis between the variable not set or too long.
As a result the variable is set with the location where geth and/or
dev tools are installed. This may override any previous set values.