[master] Merge branch 'trac991'

diff --cc src/bin/dhcp4/dhcp4_srv.cc
Simple merge

diff --cc src/bin/dhcp4/dhcp4_srv.h
Simple merge

diff --cc src/bin/dhcp4/tests/dhcp4_srv_unittest.cc
Simple merge

diff --cc src/lib/dhcp/iface_mgr.h
Simple merge

diff --cc src/lib/dhcp/iface_mgr_linux.cc
Simple merge

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

diff --cc tests/tools/perfdhcp/test_control.cc
Simple merge

diff --cc tests/tools/perfdhcp/test_control.h
Simple merge