Enable Coccinelle SmPL patches to require a specific version of
Coccinelle. In the event that the version does not match we just
inform the user, if the user asked to go through all SmPL patches
we just inform them of the need for a new version of coccinelle for
the SmPL patch and continue on with the rest.

This uses the simple kernel scripts/ld-version.sh to create a weight
on the version provided by spatch. The -dirty attribute is ignored if
supplied, the benefit of scripts/ld-version.sh is it has a long history
and well tested.

While at it, document the // Options stuff as well.

v4: Document // Options and // Requires as well on
    Documentation/coccinelle.txt.
Signed-off-by: Luis R. Rodriguez <mcgrof@kernel.org>
Acked-by: Nicolas Palix <nicolas.palix@imag.fr>
Signed-off-by: Michal Marek <mmarek@suse.com>