bug#19481: package.el: support .tar archives featuring a pax_global_header entry

[Eli Zaretskii]

> From: Ivan Shmakov <ivan@siamics.net>
> Date: Thu, 01 Jan 2015 17:55:46 +0000
> 
>       As currently implemented, package.el signals an error trying to
>       process a .tar archive which has a pax_global_header entry, –
>       such as the archives produced with $ git archive --format=tar.
> 
>       Please thus consider the patch MIMEd.
> 
>       * lisp/emacs-lisp/package.el (package-untar-buffer): Ignore
>       archive entries with link type being 55.
>       (package-tar-file-info): Consider the second file name in the
>       archive if the first one has no directory component.
> 
>       * lisp/tar-mode.el (tar-untar-buffer): Ignore archive entries
>       with link type being 55 (pax global extended header.)

What about type 72?  (See tar-mode.el for the details.)