Package rpminstall-tests-checkinstall: Information

- Marked XFAIL: non-critical unrealistic cases when obsoleting an exact disttag.
  (They are known to fail in Sisyphus in rpm-4.13-alt6. Of course,
  this requires a fix, but this is not critical.)
- Adapt for p7 and p8. (Some tests need to be skipped unfortunately, because
  even if rpminstall was able to interpret disttags, rpmbuild is not
  yet able to produce them.)
- Marked XFAIL: tests dealing with future deps with disttags (not known
  to the old rpm in p7 and p8.)

- Additionally test the same things, but provided as virtual Provides
  (dummy = ...).
- Implemented a checkinstall subpackage that runs these tests immediately.
- Fixed running the tests from another working dir.

- initial build for ALT Linux Sisyphus.