[master] Merge branch 'trac3705'

diff --cc doc/guide/dhcp6-srv.xml
Simple merge

diff --cc src/bin/dhcp6/dhcp6_srv.cc
Simple merge

diff --cc src/bin/dhcp6/dhcp6_srv.h
Simple merge

diff --cc src/bin/dhcp6/json_config_parser.cc
Simple merge

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

diff --cc src/lib/dhcp/tests/pkt6_unittest.cc
Simple merge