gnu-tar 1.28

Version bump from 1.27.1 to 1.28.
gnu-tar 1.28

This is the temporary upstream patch suggested. It didn’t seem to do
the trick on my end, but I’m going to get the bot to test it anyway to
rule out any 10.10 errors. This is an ongoing discussion, and may well
require a significant patch if this one doesn’t work. Apparently,
according to upstream, we should be seeing these xattrs errors with the
1.27.1 version as well, but clearly we aren’t, so that’s a little odd.
gnu-tar 1.28

If the maintainers are okay with this method of patching, it works on
my end and should pass the build bot. This complicates an otherwise
simple formula quite a bit, but apparently we should’ve been having
these issues from at least gnu-tar 1.27.1 but clearly, we weren’t. Not
really sure why 1.27.1 didn’t have the issues 1.28 is having, but this
patch fixes 1.28. It is reported upstream and may well end up in a
future release, but it needs to be confirmed that this patch doesn’t
break other non-OS X OS support before it can be folded in officially.
gnu-tar 1.28

Adds code comment to the PR with a link to the message thread
containing more information on the xattrs issue.
gnu-tar: update 1.28 bottle.