License clarification in messagelib #2

[Christophe Giboudeaux]

Sandro, Volker,

While converting to SPDX format, I found 3 problematic files:

messageviewer/src/messagepartthemes/default/autotests/rendertest.h for which 
you're both copyright owners,

messageviewer/src/messagepartthemes/default/autotests/showonlymimeparttest.
{cpp,h} whose copyright holder is Sandro.

These file state they are GPL-2.0-only or any version approved by KDE e.V. 
according to the GPL-3.0 license.

Problem: As these files are originally only GPL-2.0-only, the GPL-3.0 proxy 
section cannot be invoked.

I see three possible solutions:
- relicense these files to GPL-2.0-only or GPL-3.0-only or any other version 
approved by the KDE e.V 

- relicense them to something else
According to the relicensecheck script output, these files could become LGPL 
(with or without the e.V. clause)

- Drop the e.V. clause since it cannot be invoked for these files.

Christophe