Checksum validation update v1.1

See https://github.com/regit/suricata/commit/b0a5f5950c74280d844fad417f45cb453ad55fad for difference with previous PR.

PR build: https://buildbot.suricata-ids.org/builders/regit/builds/59
Bugs: https://redhttps://redmine.openinfosecfoundation.org/issues/751 mine.openinfosecfoundation.org/issues/752