Automatically increment KDevelop minor version in each KDE Gear release

If I recall correctly, the incrementing started out manual because it
was assumed that the ABI rarely changes. In practice though, I bumped
the minor version in each KDE Gear release since the switch to the
release-service-driven versioning in
b8e30215.

Calculate the KDevelop minor version based on the release service
version. If some KDevelop release is small, clearly does not change
public API and ABI, a developer can cancel the automatic minor version
change by manually incrementing the final subtrahend in the math
expression (currently 59). There is a risk that no one remembers to
cancel an unnecessary automatic version increment. But an unnecessary
version change is less problematic than a missed one.