issue with DataFileSeekableInput.SeekableInputStream.skip

We found a longstanding bug in the implementation of DataFileSeekableInput.SeekableInputStream.skip.

This skip function is not hit that often.  It can for example be hit when the FastReader is enabled and it tries to skip a significant amount of data.

The implmentation of this function is however fault and can result in data corruption or
java.io.EOFException, as instead of skipping the number of bytes, it will seek to a wrong place in the file.
 
We have a pull request ready to fix and test this issue.