[cmake,bugfix] Allow 0 as a version.

Previously we checked whether the extracted Version evaluated to
True. Unfortunately, there lazy people like me that like use a version
of 0 for testing, which evaluates to False and breaks configure.
With this patch we allow 0 to and just test wether the version consists
of characters.
(cherry picked from commit 9afabdcda991fd05de2fb889a457b8187a286086)

Signed-off-by: Markus Blatt <markus@dr-blatt.de>
[dunecontrol,release] Make warnings about superseeded modules less verbose.
(cherry picked from commit 50926312ebfa64ed97fe5e5111d14279e54e8df8)

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