added solution to the 'Unable to locate package libopus-dev' problem
Merge pull request #706 from kc1212/install_readme

added solution to the 'Unable to locate package libopus-dev' problem
A bit of tests added.
Convert IPv4 in IPv6 to IPv6 address in recieve packet.
Fixed bug with client_ping_nodes() not pinging any nodes.
Test passes now, uncommented it.
Fixed PID forgetfulness.
Merge pull request #709 from tawm/master

Fixed PID forgetfulness.
Improved onion connection by a bit.
Fixed error in last commit.

The tests actually work.
Added DHT bootstrap server info packets.

define DHT_SERVER_EXTRA_PACKETS to enable.
Fixed warning.
Fixed possible issue.
Lowered the route to friend minimum number of peers.

This fixes hole punching for some NATs.
Made onion test taste more like onion.
Fixed bandwidth issue.
added API function to get online friend count
decrement counter on friend delete
Use a more appropriate distance function for group chats.
Onion_test should be now a bit less failure prone.