[cmake,bugfix] Do use a version when there is not version in the depends or

Previously, we used >=0.0. if there was no version information in the
dependes and suggests clause of a dune.module file. This breaks with
the new more strict version checking. Therefore with this revision no
version gets set if it does not appear in dune.module
(cherry picked from commit ce8e8d474171dd4f84596b4da662d078b036de39)

Signed-off-by: Markus Blatt <markus@dr-blatt.de>