framework.SIGDescribe is better because:
- Ginkgo uses the source code location of the test, not of the wrapper,
when reporting progress.
- Additional annotations can be passed.
To make this a drop-in replacement, framework.SIGDescribe generates a function
that can be used instead of the former SIGDescribe functions.
windows.SIGDescribe contained some additional code to ensure that tests are
skipped when not running with a suitable node OS. This gets moved into a
separate wrapper generator, to allow using framework.SIGDescribe as intended.
To ensure that all callers were modified, the windows.sigDescribe isn't
exported anymore (wasn't necessary in the first place!).
