Since we need to change the form of the siggen function, we need to add versioning
and some verison checks. This means if a newer bitbake is used with older metadata
we can detect it.
(Bitbake rev: 721556568413508213d22c29985e305a45a8d68a)
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>