hexdump(1): Basic testing

[kevans]

Summary

Add some basic tests for hexdump(1)'s various output flags. Formatting
tests are omitted for this initial run as there are still some bugs to work out
there.

This covers -s flag testing on devices and non-devices that would have caught
breakage found in PR 219173 as well as other subtle breakage caused locally.

Test Plan

Run the tests as-is and with D10893 applied to address the other failures
that arise.

[kevans]

I've included three basic input files to test some corner cases: Single-line only (for most flags), column-sized aligned, and repeated lines -- I've used these in most test cases just for good measure.

[ngie]

Please MFC this change.

[kevans]

Hi @cem,

Any thoughts on this one? =)

[cem]

I'm not too familiar with hexdump, but if the tests pass and do what you expect, LGTM.

[kevans]

@cem Excellent! =) May I consider this approval for commit based on advice by emaste@ for this week?

[kevans]

w/ MFC After: 2 weeks, perhaps, since it's a low-impact/test change.

[cem]

In D11279#239604, @kevans wrote:

@cem Excellent! =) May I consider this approval for commit based on advice by emaste@ for this week?

Yep, go ahead.

I don't have any guidance on MFC timeframe, I don't MFC in general.

[kevans]

Some slight tweaks made before commit:

• Correctly denote that two test cases are currently expected to fail; I was waiting until commit to add this in case it was addressed before-hand, and forgot to note that here. =(
• Rename of *Cflag*.out to satisfy pre-commit hook naming clash detection