Fix version comparison in Version.pm

Fix version comparison in Version.pm

Version strings with unequal numbers of parts were being compared
incorrectly. We cure this by treating a missing part in the shorter
version as 0.

per complaint from Jehan-Guillaume de Rorthais, but the fix is mine, not
his.

Discussion: https://postgr.es/m/20220628225325.53d97b8d@karst

Backpatch to release 14 where this code was introduced.