sync system.tar.inc with Archive_Tar 1.4.14

Problem/Motivation

D7 has its own - slightly modified - copy of Archive_Tar at modules/system/system.tar.inc

We have pulled in a handful of security fixes in the last few years, but there have been a couple of non-security changes and bug-fixes to Archive_Tar which D7 does not have.

Apart from the fact that bug fixes are good, this also means that manually applying any security changes to Drupal's version is harder because the diff between the two contains more noise.

Steps to reproduce

$ diff Archive_Tar/Archive/Tar.php drupal-7.x/modules/system/system.tar.inc

...or use your diff tool of choice.

Proposed resolution

Let's sync as many recent changes to the upstream Archive_Tar as we can so that comparing the two versions is easier, and we benefit from upstream bug fixes.

Bonus points: we're adding more (/ some) testing of the Archive_Tar implementation in #3102159: Add tests for Archive_Tar which should help reassure us that upstream changes aren't breaking anything.

Remaining tasks

patch, review, commit, profit

User interface changes

n/a

API changes

n/a

Data model changes

n/a

Release notes snippet

I don't think this requires a CR as the changes we'll make don't change APIs etc..