Log Message:
Updated p5-Archive-Tar to 2.18.

From Kai-Uwe Eckhardt in PR 51639.

2.18  07/11/2016 (JHI)
- Capture also the STDERR when checking tar exe

2.16  01/11/2016 (JHI && CBERRY)
- Make roundtrip tar exe finding robust for crappy tars

2.14  20/10/2016
- Fix roundtrip test when tar executable is absent

2.12  16/10/2016 (KHW && JKEENAN)
- Fix pod in bin/ptar
- Distinguish between archives with/without directory entries