TNetXNGFile: update offset by the number of bytes that were actually read
TNetXNGFile: update offset by the number of bytes that were actually read

tc3t/qoot,tc3t/qoot,tc3t/qoot,tc3t/qoot,tc3t/qoot,tc3t/qoot,tc3t/qoot,tc3t/qoot,tc3t/qoot,tc3t/qoot