Sparse files handled incorrectly

[h3xx]

I noticed that Archive::Tar doesn't extract sparse files correctly, when the tarball is created using tar c --sparse -f file.tar sparse.dat

Steps to repro:

# Make a sparse file that looks to all readers to contain 10MB of NUL bytes
rm -f my-sparse-file
truncate -s 10M my-sparse-file

# This must return 0 or you're likely on a file system that does not support
# sparse files.
du my-sparse-file

# This should give the logical file size, 10,485,760 bytes
ls -l my-sparse-file

tar c --sparse -f tar-with-sparse.tar my-sparse-file

# This, likewise, should give the same number of bytes as ls(1)
tar tvf tar-with-sparse.tar

rm -f my-sparse-file
perl -MArchive::Tar -e 'Archive::Tar->extract_archive("tar-with-sparse.tar");'

The my-sparse-file will be created with a 0-byte size (should be 10,485,760).