Update semidp.tst for compatibility with future GAP version

[wilfwilson]

I have created PR gap-system/gap#3053 for GAP, which adds additional properties that are transferred from the factors of a direct product to the direct product, at creation.

This means that, once this is merged, many direct products will know more about themselves at creation than they currently do. This means the test output in semidp.tst and semidp.xml needs to be updated. However, since we still need to support previous versions of GAP, we can't just update the files with the new output. We have to make sure that the properties are definitely computed before viewing the direct product, and showing the new output. That's why there are lots of new calls to IsRegularSemigroup, etc.

The tests on the GAP stable-4.10, 64-bit Travis job will fail until #565 is fixed and merged.

[james-d-mitchell]

@wilfwilson rerunning the CI now.

[wilfwilson]

The corresponding PR for GAP has been merged, faster than I expected, so I think I have to merge this now to stop the Travis tests going crazy.

[olexandr-konovalov]

@wilfwilson this should NOT go to Semigroups release intended for GAP 4.10.1, isn't it?

[wilfwilson]

Thank you for the concern @alex-konovalov, but you are mistaken, this PR hasn't broken backwards compatibility. Semigroups remains compatible with GAP stable-4.9, stable-4.10, and master branches: see for instance https://travis-ci.org/gap-packages/Semigroups/builds/459705352 which is a build containing the current stable-3.1 branch of Semigroups (into which this PR has been merged). You can see that we test against stable-4.9, stable-4.10, and master, and the tests are (I hope!) passing for all of those.

[olexandr-konovalov]

@wilfwilson thanks, that's reassuring!