[master] Merge branch 'github54' (various changes)

diff --cc src/bin/dhcp4/tests/get_config_unittest.cc
Simple merge

diff --cc src/bin/dhcp6/dhcp6_messages.mes
Simple merge

diff --cc src/bin/dhcp6/tests/get_config_unittest.cc
Simple merge

diff --cc src/lib/dhcpsrv/alloc_engine.h
Simple merge