Flagging an old version should not flag newer versions

[heftig]

When, e.g., gnome-backgrounds 48.2.1-1 in [extra] gets flagged out-of-date, this should not also flag gnome-backgrounds 49.0-1 in [gnome-unstable].

I guess flags should only spread to "split" packages of the same pkgver.

[jelly]

Makes sense, we can easily test this by creating a [testing] pacakage which a higher pkgver then a [core] package and then flagging the [core] package should not flag the [testing] package. But vice-versa should.