Warn at failing overrides
Fixed two SQL queries that broke since NULL -> nullptr replacement
Single xml solution

Mana-mantis: #506.
Bumped the protocol version to 3

Version 2 was on the lpc2012 branch. With version 3 the lpc2012 and
master branches use again the same protocol.
Merge branch 'master' into lpc2012

Conflicts:
	src/common/manaserv_protocol.h
	src/game-server/monstermanager.cpp