Removing SCCS Ids from legacy code

[Alistair Crooks <agc%netbsd.org@localhost>]

The core team has looked at the question of deleting the SCCS Ids from
legacy code in our repositories, and found that there are no
appreciable benefits, and some real losses; some people actively use
these identifiers often enough for them to be needed, especially when
merging from other repositories.  None of these other repositories has
yet to delete SCCS Ids from their copies, either.

However, the preprocessor conditionals surrounding some SCCS Ids can
be simplified without any loss.

Alistair Crooks
On behalf of the core team