At the moment, tarfile.py is only able to read one
extended/special header (such as GNU longname etc.) at
once from an archive. In some cases there may be more
than one special header to process, e.g. an archive
member that points to a long linkname itself having a
long name, or a GNU sparse file member with a long
name. In those cases tarfile.py will fail to read that
particular member including all following ones. The
attached patch fixes that problem plus some minor
things that I came across while fixing it:

- fixed/improved handling of extended/special headers
in read-mode (adding new extended headers should be
less painful now).
- improved nts() function.
- removed TarFile.chunks datastructure which is not
(and was never) needed.
- fixed TarInfo.tobuf(), fields could overflow with too
large values, values are now clipped.

The patch is made against 2.4a1 sources.

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Applied to CVS HEAD; thanks!