VCS-* field update: almost there

The XS-X-Vcs-* field idea seems to have been liked by a lot of people who started adding the field to their packages, despite it being only announced on this blog (oh, you're right, and a bit flamed on d-d too :-), sorry for that).

Since then I patched the PTS so that also XS-Vcs-* (without the middle "X-") is supported. This way the field seems a bit more official, please prefer that form in your packages. At the next pulse of the PTS web interface you should be able to see the result looking at packages like polygen and tagcoll2 which Enrico (thanks!) kindly offered as test packages for the new, supposedly final, naming.

People who started using the format I formerly announced don't have to worry, it is supported as well for now. Of course changing it to the new one would be better.

As a side note I also decided to keep this name, in spite of some different proposals on d-d, since no consensus on changing was reached.

The last bit missing before an overdue announcement on d-d-a is documenting the field. The appropriate place for that being the Debian Developer's Reference, since it already contains the documentation of the other PTS stuff, I just submitted #391023 with a patch documenting the field.

As soon as I'll have feedback from the devref guys I will announce it properly on d-d-a, I swear.