Refuse plugins from a new minor version (e.g. 4.13 plugins in 4.12), but not...

Refuse plugins from a new minor version (e.g. 4.13 plugins in 4.12), but not from a new patch version.

So I can load 4.12.1 plugins (parts) from a running 4.12 konqueror,
due to recompiling KDE SC in a running KDE workspace, without the dreaded
error message about the part being newer.

The chances of a 4.12.1 plugin needing a new method in kdelibs are rather
small, and then it will fail *only* in these cases, rather than for everything
everywhere.