Detect Plasma 6 desktop

Add detection for Plasma 6, which is currently in development stage.
With the following plasma-workspace commit [1] in place,
KDE_SESSION_VERSION is set to 6, so use that to detect it:

commit 4c2242d7dfafac161baec3ec316af24d7b48ef8b
Author: Michael Weghorn <m.weghorn@posteo.de>
Date:   Thu Jun 22 07:47:31 2023 +0200

Set KDE_SESSION_VERSION to 6

Since the master branch is based on Qt6/KF6 and will
become Plasma 6, set KDE_SESSION_VERSION to "6".

This will allow other applications to detect they're
running in a (preview of a) Plasma 6 session and react
accordingly.
(E.g. LibreOffice can use this to choose to
use its upcoming kf6 integration by default instead of the
kf5 one.)

[1] https://invent.kde.org/plasma/plasma-workspace/-/commit/4c2242d7dfafac161baec3ec316af24d7b48ef8b

Change-Id: I5a15ad1fb177721fbfa016139c56a08b228f2e1f
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/153437
Tested-by: Jenkins
Reviewed-by: Michael Weghorn <m.weghorn@posteo.de>

0 files changed, 0 insertions, 0 deletions