The p2p packages can now be configured to restrict all communication to
a certain subset of IP networks. This feature is meant to be used for
private networks.

The discovery DHT contains a number of hosts with LAN and loopback IPs.
These get relayed because some implementations do not perform any checks
on the IP.

go-ethereum already prevented relay in most cases because it verifies
that the host actually exists before adding it to the local table. But
this verification causes other issues. We have received several reports
where people's VPSs got shut down by hosting providers because sending
packets to random LAN hosts is indistinguishable from a slow port scan.

The new check prevents sending random packets to LAN by discarding LAN
IPs sent by Internet hosts (and loopback IPs from LAN and Internet
hosts). The new check also blacklists almost all currently registered
special-purpose networks assigned by IANA to avoid inciting random
responses from services in the LAN.

As another precaution against abuse of the DHT, ports below 1024 are now
considered invalid.

The new package contains three things for now:

- IP network list parsing and matching
- The WSAEMSGSIZE workaround, which is duplicated in p2p/discover and
  p2p/discv5.

utils: bump stable 1.5.1

build: set GO15VENDOREXPERIMENT in env.sh

This should fix the 'make' build with Go 1.5.

les: fixed logging

Dockerfile revamp

The jit config options are not handled, but random selection still took
place, printing confusing messages.

README, VERSION: update for 1.5 release

utils: unstable 1.5.1

utils: stable 1.5.0

build: master is unstable

travis.yml: upload to the real PPA

travis, build: further maven and gpg refinements

travis, build: fix mobile build issues on travis