fix reading of extended mode Code 39
fix reading of extended mode Code 39

git-tfs-id: [https://tfs.codeplex.com/tfs/TFS05/]$/ZXingNet/trunk;C90313

micjahn/ZXing.Net,micjahn/ZXing.Net,DHMechatronicAG/ZXing.Net,micjahn/ZXing.Net,DHMechatronicAG/ZXing.Net,DHMechatronicAG/ZXing.Net