fails:IO#seek sets the offset
fails:IO#seek converts arguments to Integers
fails:IO#seek does not accept Bignums that don't fit in a C long
fails:IO#seek raises IOError on closed stream
fails:IO#seek moves the read position relative to the current position with SEEK_CUR
fails:IO#seek moves the read position relative to the start with SEEK_SET
fails:IO#seek moves the read position relative to the end with SEEK_END
fails:IO#seek moves the read position and clears EOF with SEEK_SET
fails:IO#seek moves the read position and clears EOF with SEEK_CUR
fails:IO#seek moves the read position and clears EOF with SEEK_END
