[PATCH] fast importer for SCCS files

The attached patch implements an importer for SCCS files using
git-fastimport.  It's unidirectional SCCS->git.  This is my first git
patch, so apologies if I have done something the wrong way with regard
to how one shoudl submit a patch.    I've attached the patch because
my mail client would probably screw the formatting up if I just pasted
it :(

Thanks,
James.