moved stuff that belongs into ping.[ch] there

DHT.*, ping.*:
- moved stuff from struct DHT into struct PING: toping, last_toping
- moved functions add_toping(), do_toping()
- made id_closest() publicly accessible
- send_ping_request(): killed (Net_Crypto *c) parameter in favor of copying it into (PING *) on new_ping()

group_chats.c:
- killed local 1:1 copy in favor of DHT.c::id_closest()
Fix bug.

This makes it build on OS X again...
Fixed typo.
Fixed windows build.
Possible bug fixed.
Possibly fixed the weird disconnecting/reconnecting bug.
Fixed possible bug.
Fixed bug where hole punching was attempted even though the
clients were connected.

Increased the number of ports tried per interval of time.

Also astyled the files.
Possible bug fixed.
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.
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
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.
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.