Issue #901: Sparse files with long name get renamed.

Issue #901: Sparse files with long name get renamed.

The original ustar header has a 100 character limit for the file name.
With the POSIX interchange format, an additional header attribute
contains the full path and libarchive tries to cut it to something
sensible. The GNU sparse file extension on the other hand also likes to
mangle the ustar header field to include a marker and contains yet
another attribute for the original path. If the name was truncated
earlier, this attribute would get the incorrect truncated name.