Include all files required for building in the tarball.

A couple of private, no-inst headers and the versioning linker scripts
are needed to build ivykis, so include them all in the tarball.

Reported-by: Peter Czanik <czanik@balabit.hu>
Signed-off-by: Gergely Nagy <algernon@madhouse-project.org>
Signed-off-by: Lennert Buytenhek <buytenh@wantstofly.org>