Fix one call to the now-trusted constructor for Offset, to check the value during serialization. (No unit test, as it's simple code but a pain to test.)
Fix one call to the now-trusted constructor for Offset, to check the value
during serialization. (No unit test, as it's simple code but a pain to test.)

malcolmr/nodatime,malcolmr/nodatime,zaccharles/nodatime,zaccharles/nodatime,nodatime/nodatime,zaccharles/nodatime,zaccharles/nodatime,zaccharles/nodatime,BenJenkinson/nodatime,malcolmr/nodatime,zaccharles/nodatime,malcolmr/nodatime,jskeet/nodatime,BenJenkinson/nodatime,jskeet/nodatime,nodatime/nodatime