Updated fsfsverify tool

A recent Subversion user had troubles with the middle of their svndiff stream becoming corrupt. Thanks to his openess, and sharing of the corrupted revisions, I was able to verify that it is the same issue as the one causing the read length line error. I was also able to update fsfsverify to attempt to fix this issue too. If you’re suffering from a similar problem, you might want to download the new version and give fsfsverify a try.