C++ port: UPCEAN reader fixes
C++ port: UPCEAN reader fixes

 - make UPCEANReader fail if there's no quiet zone after the end marker, vastly reducing UPC_E false positives

git-svn-id: d565a5fbffec933846bf643895bf9c245569575b@1495 59b500cc-1b3d-0410-9834-0bbf25fbcc57

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