Tests of state loading/saving lead to two fixes for DHT.c and util.c

util.c:
- fix for not properly parsing an empty section (data length = 0) at the end of the state, showed as bug when having no ever valid clients (DHT) or an empty name (Messenger)

DHT.c:
- fix in saving less data than originally announced, showed as bug when not having reached any clients ever (no clients or only with timestamp of zero)

messenger_test.c:
- tests for load/save of DHT and Messenger
- signed/unsigned warning fix

Messenger.c:
- added break; in empty default: (didn't compile for me without, when DEBUG not defined)