Ported r2692 from ZXing

Original commit message: "Add warning about test text files that may
have a spurious newline"
Small performance improvement to ZXGenericGF
Ported r2693 from ZXing

Original commit message: "First take on Guenther's updates for PDF417.
Still need to investigate test suite #2 failures"
Ported r2694 from ZXing

Original commit message: "Images to accompany last commit"
Ported r2695 from ZXing

Original commit message: "Fix an NPE that comes up in full testing from
last commit"