[v4] Fix strptime era handling, add more era tests [BZ #24394]

[Carlos O'Donell]

On 3/31/19 3:20 PM, Florian Weimer wrote:
> * Carlos O'Donell:
> 
>> .. and tst-strftime2.c is hideous, a terrible test with no comments
>> whose logic cannot be followed.
> 
> I think it's not too bad.  It's one of these combination tests.  I
> can't read Japanese, so I have trouble understanding what it exactly
> tests, but any test trying to get coverage like this will looke pretty
> similar.

The lack of comments makes the test difficult to maintain.

My objection is not to combinatorial tests that auto-generate the testing
matrix, in fact you've shown that such tests are possible with good comments :-)

My usual review of these tests begins with: "Please add more comments."

You eventually forget why the test generates the permutation in this way or that.
I also support the heavy use of enums to make the test intent perfectly clear.

-- 
Cheers,
Carlos.