Fix bug/add test coverage for SDLTest_GenerateRunSeed helper; improve test harness adding output of repro steps for failures; improve negative test for SDL_GetError/SDL_SetError
Disable Wayland/Mir again for 2.0.3; it's a quick, brown-paper-bag release.

We'll enable it by default for 2.0.4. Hopefully.   :)

    ( http://www.catb.org/jargon/html/B/brown-paper-bag-bug.html )

--HG--
extra : rebase_source : 30eae3abc592f26538584fefcaf2dd49be3cfa89