expanded Client_data to hold two addresses (IPv4, IPv6) instead of one

Compilerflag: CLIENT_ONETOONE_IP (to define in DHT.h, default unset i.e. NEW case: two addresses)

Every function in DHT{_test}.c working on Client_data has been rewritten to store IPv4 addresses in assoc4, IPv6 addresses in assoc6.
Loading/Storing of states defined with other compiler switch is transparently adjusting to the differences.

DHT.h, DHT.c:
- introduction and handling of the structure changes

DHT_test.c, Messenger.c:
- logging adapted to new structures

util.h:
- LOGGING isn't undefined per default anymore
Permit -Wshadow as useful warning.
Merge pull request #606 from FullName/Permit.Wshadow

Permit -Wshadow as useful warning.
minimalistic increase in elegance ;)

DHT.c:
- loops over assoc4/6 slightly more elegant
Logging loop corrected.
don't lose globally valid addresses for locally valid ones
Merge branch 'ClientData46' of https://github.com/FullName/ProjectTox-Core into FullName-ClientData46
Astyled the code.
Fixed possible problem.
Update INSTALL.md

Included git in the apt-get so that new users can use the necessary git clone command.
Merge pull request #608 from Nominate/patch-5

Update INSTALL.md
friend_iplist and route_tofriend behaviour fixes.
LAN ips can be sent to LAN ips.
Behaviour with LAN ips is now better, also fixed possible bug.
Fixed small issue.
Merge branch 'FullName-ClientData46'
Connection bug fixed.
Fixed possible bug.
Potential DoS fixed.
Fixed possible problem.