[master] Merge branch 'trac4121' (RAI option packed last)

# Conflicts:
#	src/lib/dhcp/libdhcp++.cc
#	src/lib/dhcp/libdhcp++.h

diff --cc src/lib/dhcp/libdhcp++.cc
Simple merge

diff --cc src/lib/dhcp/libdhcp++.h
Simple merge

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

diff --cc src/lib/dhcp/tests/libdhcp++_unittest.cc
Simple merge